Do larger trim plates aid in extending the length of the hull? If so, could you use this for control at faster speeds?

I've seen numerous posts on all the forums that state length of the hull is what determines the speed threshold and controllability. However, what you said about the footprint or "ride pad" dimensions seem to make more sense in determining speed threshold.
I guess you could always add balast to the bow to prevent blowover?

well trim tabs are used for porpoising hulls
If you think about it then they kinda are a extension of the hull. But it is not counted in the length. It is from the bow to the stern and nothing else.
But as for ballast most people just more the batteries or use the trim tabs. I would also try a wing so that when going slower yo do not have that ballast but when faster you have more down pressure.
kinda

Well, the reason I ask is this. If you have a 27" hull, and many say the limit is 45mph for reasonable control with stock 1" trim plates, by increasing to 1.25" or 1.5" you might extend that speed limit a bit more and improve control.

You mentioned a spoiler. How about a adjustable canard?

Also, wouldn't longer turn fins and rudder improve controlability with the higher speeds?

well a canard is a good idea. But the problem with that is if you were to use a servo to change the pitch then it would be pointless because you wouldn't be able to adjust it fast enough to control your flip.
As for the turn fins. Most turn fins on a mono do not touch the water when you are going straight. So i don't think that they would help

Thanks.
Yeah, it would be pointless to put longer turn fins because it would add more drag on the straights. Didn't think about that one. Try to fix one area and you better watch it......or you'll hurt another.

I never said it would do 45 anyway, just thought it would be cool if i did. im gonna put trim tabs on it so it is more controlable and turn fins. itll prolly do 30-36 with the cf props im gettin. also is the a way to cool the batterys? I am runnin a 48mm cf prop and people were sayin thet it makes the batterys really hot. i didnt think there was a way but just askin anyway.

I replied in the prop thread for you. Your pretty right on about speeds. 33-36 dpending on your setup. Get ready for some croc roles and hooks if you cut her to quickly. But you will have a blast with that prop. Bar cut and detongue will help handling more.

thanks a lot