I have a 7.5 lbs Edge 540T .60 size with a 2 stroke .77 in nose. It is turning a 14 X 6 @ 10,300 on a APC. And about the same with a Top flight wood 14 X 6. I prefer the wood props because they have instant throttle response and it makes hovering much easier to adjust with.

The way it is set up now I can hover a little more than 3/4 throttle and at WOT it pulls out but very slow. Flying around is at an okay speed but I am not really concerned with speed as I am doing some 3D.

I tried using a APC 15 X 4 and it was much easier to hover but the prop weighs so much it revved much slow and just killed my throttle responses in hover. I haven't been able to find a wood 15 X 4 yet so haven't had a chance to see how one of those would work. I am guessing much better than the APC since its much lighter.

Anyways I am really looking for a 4 stroke to put in nose. I was looking at the Saito 100's but the say APC 14 X 8 @ like 9,300 from their site. Not sure what it would spin a 14 X 6 at since I don't have one. My question is if it does spin at about 10,000 would I be getting any gain from my 2 stroke going to this 4 stroke? It kind of seems it would be the same.

The only advantage I could see is maybe putting a 15 X 6 or 15 X 5 or so on it. I am just looking to get a lot more thrust than what I have now.

What should I go with? 100 4 stroke or s bigger 2 stroke?
I want to be able to hover with a good amount of throttle left over. Say about hover at 1/2 or so with my 7.5 Edge.

IMHO 7.5 lbs is to much for anything less than a strong 90 2 stroke. I would be looking at an 90 2 stroke on an ultra thrust or some such, or a YS91/110.

I was looking for an engine that would swing a larger prop than what I have. Really looking for it to be way powerful enough hovers but not to heavy. I don't want to kill the characteristics of the plane.

You probably don't want to use a 14X8 using in a Saito 100 for your application .... You should be looking at a 15X6 prop wich will give you a considerable amount of thrust increment and will still rev fast enough for hovering maneuvers.

My Saito 100 revs a 15X6 @ 9400 rpms which equals almost a 1:80 power to weight ratio in a 7.5 lb airplane.