ORIGINAL: gerryndennis
.......Spoilers work well with positive G, poorly with negative G, and not at all at zero G.......
I'm not sure I agree with this totally. Take the case of spoilers on an Ugly Stik that is upside down. Spoilers positioned more towards the trailing edge ala P-61 and MU-2 would have some tendency to act as lift flaps in such a case so it would roll back upright.
However I'd be the first to suspect that the rolling action under the different G conditions will not be consistent. As such I agree that they are best used on airplanes that will no find themselves upside down or otherwise negatively loaded except under dire circumstances.
As modellers who can easily overbuild and over power our designs we often forget that full sized aircraft operate under very confined load and speed envelopes that we do not. The B-52 model video noted earlier along with the related Fairchild base full size B-52 crash that I found in the related videos shows what happens when you ignore or get tossed out of that envelope by circumstances. Using spoilers for roll control in model applications has some possibilities for some specific types of design but obviously it isn't something you want to use for all styles of model. As gerryndennis closed with it's about compromise and choice.