ORIGINAL: crankshaft
if 30% is okay and I run 20, I could probably increase the conpression then. it would definetly help the response, and increase the efficiency of the engine. that could be almost as good as running more nitro. but then again could it possibly slow burn rate at high rpms, or at that, is it possible for a 2 stroke to have detonation before top dead center? frost, is that why you say to step down on the glow plug? i ask because you seem to know what you are talking about. I would trust your jugement over most.
A few things... The stock 25 comes with 3 shims, I have found that virtually anyone on 20% or lower can safely remove 1 and most (but you're on your own here) can remove 2 even at 20%. There is a slight increase in power gained by the added compression, and many people say this also makes the truck easier to start.
This does not by any means come close to adding 10% nitro to your fuel though. Most all big-blocks can safely run 30%, the manufacturer's steer you into a safety cushion at 20%... The stock 25 (again, as with most BBs) can run 30% nitro with a McCoy mc59 or an OS A5 or other equivalent heat range safely. The 30% race makes the most power, and this is easily visually verified. Whenever you change fuels you will have to retune. If you go up in nitro the engie will run VERY cool and have to be leaned out.
Pre-ignition/detonation can occur in 2 strokes, it can range from annoying and power-robbing to destructive (bent rod, rod that fails at the crank, etc). Obviously if you pull a few shims off of your 25 don't jump to 30%, but it can be run just fine with the stock shim arrangement.