Tim, with most Ni-starters are only1.2 volts. This voltage works well on your average plugs until you start using them on Cox, Norvel, Nelson plugs. The cold is another factor which even adds more complexity to the problem. Nelson plugs especially desires a strong battery in order to get a decent start. Initially they work fine and its probably due to holding a surface charge which dies off after a few starts. I was using a Mcdaniels Ni-starter with the Sullivan adapter for 1/2 a usage. I found this set up to be more troublesome then helpful. I was always under the assumption the clip was shorting out. It would work fine on the plug but wouldn't work when I put the adapter in it. I've replaced most of my plugs and adapters with 16 ga. lamp cord. I found that there is too much resistance in the wire due to the light gauge they use. The standard Cox clip is horrible for this problem and works well when the wire is beefed up. I prefer to use the old standard of linking 2 hobby batteries together and hold them together with nylon wire ties. I get a year of usage using this method and I fly almost every weekend. I gave up on the Ni-starter when I was using it on a .40 size plane when I disengaged it popped off and went into the prop. I almost lost my teeth from it not to mention it flew over 75 ft. Some of our club members solder several d-cells together as an inexpensive method which works very well. Another member made himself a small box which is approx 2" tall x 6" wide in which he can open and replace the d-cells. He uses a brass strip and some springs to hold the cells with 2 terminals coming out the top. Ken

This is what I have been using for several years.  I got it when I was racing R/C Pylon and it lites Nelson plusg just fine.
http://www.radiosouthrc.com/pro_driver_mkii.htm
It has a removable standard glow plug adapter that can be swapped pot for a 1/2A clip.  It is a little pricy but it will light a loaded up plug in and inverted application.

I use 6 D cells soldered together with duct tape to hold things together.  Cheep to build, never need charging and mine lasts 2 to 3 years.  However I must admit I don't fly all that much. O yes I use banana jacks and heavy wire.

If you want to build a nifty starter box to hold battery, power panel and a variety of stuff in a very compact form, RSM Distribution has a laser cut kit.  Several of us use it locally, and it holds your clips, 1/2A starter and fuel syringe.  All you need at the starting line.  I like the 1/2A clips from 4-Pi, but I think Du-Bro makes a larger one that works just as well, or maybe better.  Heavy lamp cord is the ticket, no matter what battery/clip combo you use.

Since my gel-cell is dying, I have made up a Ni-starter using a 2000 mah Ni-cad, 6" of cord and the 1/2A clip.

One caution:  I used a transistorized power panel for years and loved it, but it failed and I burned out about $20 in plugs figuring out that the panel wasn't working anymore and was putting 12 v on my plugs!  I now use a cheaper one with a simple pot and meter.  Not as cool, fewer features, but less likely to fail.

I plan to make up a 12v pack of AA NiMh cells (2000 mah) from Harbor Freight.  A little more expensive ($27 vs $20) than a new Gel Cell, but WAY lighter.  It will need more frequent charging, but the peak current output may be improved.

OK.  Finally got the necessary round tuit.

With a pair of alkaline 'D' cells in parallel, 18-gauge (or maybe 16) and a Sulivan clip, things started right up.  With a bit of cylinder swapping, I even got a high power run.  Tee hee!  Now if only it'd stop raining...

I did add some heat shrink to the top of the Sulivan clip (the part that engages the button on the head) -- the two bits of metal were awfully close together; the heat shrink should keep things from getting mashed together too easily.  Maybe I'll build a holster for the clip, but if it works...

Just recently solved at least part of the problem...

...I used the charger cord from a defunct charger. You know, the one that simulates the contacts to a glow plug? Trimmed the cord to a handy length, about 20" and mounted a Du-Bro 1/2A Kwik-Klip there. Solid connection seems to be important in getting the juice into 1/2A engines' glow plugs.  The coiled "adapter" plugs into the Ni-Starter, and the Du-Bro really bites on to the plugs, whether Cox, Nelson, NorVel or standard 1/4-32 screw-ins... And it does not 'dedicate' a Ni-Charger to only 1/2A plug heads...

Since the charger had died, this cost me only the price of the Du-Bro klip, which I had for years, anyway.