Maintaining the center of gravity at the plan location should not be your first consideration in choosing an engine.
There has been a huge amount of discussion on engines, engine runs, and engine sizes in this forum over the years. I suggest that you do a search on "engine" or "engine size" (with quotes) and see what pops up.
If you have a stunter of "normal" proportions (i.e., airfoil thickness, aspect ratio, etc.), then the amount of power you need from the engine is going to be determined by the engine size -- BUT -- if the plane is too heavy it'll never fly right, and there's a contingent out there that feels that if the plane is too light then it'll be a great fair-weather plane, but won't be happy in the wind.
Having said all that:
The Fox 35 is what the Twister was designed for, but most folks feel that engine technology has marched on. Your best bet in a Twister is to put an LA 46 in it, and adjust the needle setting until you like the performance.
(I highly recommend finding a set of plans for Fancherizing your Twister. Folks feel that airframe technology has marched on, too, and that a Twister makes a great starting point for a stunt training with good modern "numbers". I know that I'm doing very well indeed with my rather overweight Fancherized Twister; I'm past due to be moving up to advanced with it.)
Note that there are plenty of people out there who disagree with me on these -- I'm just kind of distilling the zeitgeist, and presenting it through a lens composed of my own meager experience. You'll find plenty of people who think that useful engine development stopped at the Fox 35, that way heavy (or way light) planes fly just fine, etc. -- part of learning stunt is to learn how to separate the good suggestions from the bad, and who in general makes good suggestions and who doesn't.