When Bob Zambelli shows up, he will tell you that even a Tim 4 isn't needed! Even Floyd says that if you want a real lightweight system, then use one of "Samchamps"  (Larry Davidson) lightweight coils and a small LiPo, not forgetting the capacitor across the points!
If you have an oily points regime and the contacts are model size, then a solid state switch does have lots of advantages. I have been playing (and I emphasis playing!) with a microprocessor controled solid state switch. It can do lots of fancy things, like limit your top rpm, time your engine run and give a readout of rpm. It can cut off the battery supply when the prop stops rotating, alter ignition timing during the run and on and on...... You can even programme the processor to recognise points bounce and compensate for this nasty phenomena.
Mind you no one really wants the added complication of such a set up for control line stunt. I certainly do not! Keep it simple is the best advice and decide if you are in Bob or Floyds camp re using transistor ignition! I just play and enjoy the programming side of the processors and apply it to old time spark engines for fun. I was greatly aided by a friend of mine who makes processor controlled ignition circuits for racing motorcycles. I would never have been smart enough to do it by myself!

Regards,

Andrew.

There are numerous advantages using a transistor coil driver/switch.  The recent VSC in Tucson featured an OTS event using spark ignition.  Reports were that good engine runs in spark ignition were common.  Compare this with the unreliable operation of years ago, before transistor coil drivers.

  And reliable batteries, and, no 12-year-olds trying to solder them up!  I would wager that careful adults with standard parts can get a pretty reliable results compared to the good old days.

    Brett

My recommendations are use good, hi capacity AA NiCds, make all wiring as short as possible, in thick flexible wire and make sure that your solder joints are top rate. Also Make sure that your on off switch is capable of switching the currents involved without a significant volt drop. You only have a very low voltage across the battery in the first place, so you cannot afford to lose any voltage at bad joints!
If you use say an OK Super 60 (a la Bob Zambelli) then the points are up to automotive standards (I use Nissan auto points on mine!). This means that you are unlikely to get much volt drop across the points (compared to minature points you see on a lot of engines). With the OK engine, the points are at the back and don't tend to get oil soaked.
For minature points at the front of an engine, I would use a transistorised unit to be on the safe side. You can't go wrong with Floyds's circuit, there are plenty of other designs about that work reasonably well. If you are new to the game, use Floyds, then you cannot go wrong.
Almost as important, make sure you have a good plug, most of the old Champions can leak and cause all sorts of problems. Take a look at Bob's writeup on his Super 60, lots of excellent tips there.
Our small Kettering system is in fact a form of CDI ignition. The turns ratio on our minature coils are only several hundred to one, with around 3volts LT available, this would only give a few kilovolts at the plug, insufficient for a spark. The back emf generated by the coil (when the points break) is sufficient to charge the capacitor up to 200 to 300 volts, this is then dumped across the LT winding of the coil and with the turns ratio as it is, this gives the 20 kilovolts or so across the plug and hence the spark. So a good high voltage capacitor is required! I suspect I may be challenged on this interpretation of events. However anyone with a storage scope can see these high voltages across the capacitor.
For control line use, the addition of microprocessor control is a waste of time. Mind you for radio assist, old timer flying, it is great to retard the ignition by applying a voltage from the reciever output directly to the processor. This eliminates a servo to actuate the mechanical advance retard. This is just me enjoying playing with processors. For control line flying, use the KISS principle! Or a variation on Occam's razor principle, keep things to the necessary minimum and there is less to go wrong!

Regards,

Andrew.

Hi Chris,
           NiMh batteries should work, but I do not think that they have a really low internal resistance like a NiCd. Sorry, in plain English that means that they can deliver less current than a NiCd for any given situation. So why handicap yourself? I would go for really good quality, high capacity AA NiCds any day of the week.
  Regarding your Bantam, I really don't know. I have a Bantam that I run sometimes, so I will go and take a look............................Hm ....it is a non original NVA. Looks as though it is a small Enya or maybe an OS setup. Looking down the rear intake, I can see no sign of a hole in it, therefore most likely to be a single hole facing towards the front of the engine. Could be a double hole too, with the holes at right angles to the axis of the intake tube. I am loath to disturb it as there appears to be a very complicated series of nylon washer and some form of adhesive, presumably to prevent any leakage. If I were you, go with the manufacturers recommendation. The engine should run irrespective of the position of the hole in the spraybar. Some engines just run better with the hole in a particular orientation. This is usually when you rotate the spraybar and just lose sight of the hole (single hole spraybar). With a two hole version, I usually end up with the holes in equivalent positions, either side of the spraybar.

Good luck with the Bantam!

Andrew.