@DoneByDan & @Heathen Viking attached is the template for the barrel. As far as the length to the barrel use, as i mentioned on my instructions:
"When i printed the template exactly at 100% it didnt fit right around my tube, so i reprinted at 144% (crazy right, maybe its the printer lol. just make sure when you print you print and print until it fits perfect) but it fit perfectly after. tape it on so you can use the template without it moving."
As far as the originals go, the barrel from base to muzzle should be about 8 inches.
@DoneByDan, can you ellaborate on your question for the electronics? i thought my thread spoke of what i did, but i can answer anything that was unclear.
hope this helps!