A few more ideas/opinions on lines:
1. You can use the original Dacron lines and have fun. They seem to make up about 26' lines if you use one full bobbin. They are draggy (but pretty durable and fool-proof since they do not kink) so even though they are short, they tend to slow the plane down for a more manageable rotation rate. One of the guys that occasionally flies at our field flies these and the rotation rate is pretty high when the engine is fully leaned out--or when the setting goes lean near the end. He is prone to getting a bit dizzy. Possibly important is that these pretty much tolerate getting walked on or even tangled and knotted if you can straighten them out again. This would appear to only be true for Dacron.
2. Spectra lines have the same advantages as Dacron, but are not nearly as draggy. I have a Lil' Satan with a more or less stock Black Widow. This is a two port engine, and with a 6-3 prop on 26' of spectra, and it moves right smartly. Two guys that hadn't flown in years tried it and managed, but nearly got screwed into the ground. Go read up on the right fishing knot to use on spectra, as the knot at the terminations is the weakest part of the lines. Quick and easy. (I really like using the same material for "figure 8" hinges on elevators--from 1/2As up to 40-sized racing planes. Extremely low friction, incredibly strong, quick and very inexpensive.) The last spool I bought for 1/2A lines and hinges was Power Pro 30 lb test ("8 lb equivalent diameter" compared to monofilament.) I'm sure there are different brands and different sizes available. That is just what I picked out. If I recall correctly, the line testing indicated that the true breaking strength for tied control lines was about 1/2 the box rating, so for 1/2As this would give about 15 lb per line. Since the pull tests are 5 lb for stunt and 7 lb for racing (again, from memory) you can see there is still large safety margin if correctly tied and in good condition.
3. Using .008" stranded steel lines allows longer lines and less drag but they are fragile and have to be handled carefully. Kinking them is all too easy and they are scrap. Walking on them generally scraps them too. They cost more than Dacron, and more than spectra unless you are able to use the fishing line for either lots of line sets or, go imagine--fishing! It isn't worth it to try to wrap line ends on .008" wire, but really small aluminum crimp sleeves make terminating the ends easy. I would not recommend the larger copper sleeves used with bigger lines. You can get appropriate sized sleeves from fishing suppliers or one of the control line suppliers such as Melvin at MBS. I tend to use 42' steel lines on nearly everything because it seems to work fine, and I can reduce the number of lines in the box to something manageable. Currently flying a Baby Clown, Baby Skyray, a Wizard-like trainer, Stop Sign platter, and mostly everything but the Mouse racers on .008x42's.
4. Solid steel lines (not stranded) are used in .010" diameter for 1/2A Mouse racing. These have their own special care and handling needs, and are also pretty small and fiddly to create the end terminations. They are formed (double looped), wrapped and soldered and then cleaned and oiled. Note that soldering the terminations on stranded lines can quickly result in broken lines from overheating or corrosion. This even happens to some very competent builders, so be aware of the issues if you try this technique. It was interesting to recently see that Bob Hunt of Control Line Specialties was offering some .008" solid line material to the control line community. I'm still thinking about the advantages and disadvantages of this opportunity. Maybe I'll try some to see if I like it!
Good luck and hope you have fun building soon!
McSlow
PS--Be sure to avoid a full-size control line handle if it has "flexible cable" such as the old Hot Rock. The pull from a 1/2A plane can't really straighten the cable out so the controls are mushy and seem to have no defined neutral. The Cox-style plastic handle works with Dacron, and can be modified slightly to work great with spectra or steel lines.