I'm considering buying a -2 shorty for my 21 foot Schiada but am not all that familiar with them. Is there a rule of thumb on speed gains from converting to a shorty ? I've also read this can cause issues getting on plane. Currently the boat spins a 26p and runs 75-78. Any and all info on a shorty is greatly appriciated.

I suggest you call Schiada and see what they recommend. My guess is the current drive height is likely close as it looks like you already have a Bravo 1 prop. Assuming your drive height is close, BBLADES might be able get you an additional 1-3 MPH.

Why don't you find someone that has one and try it on for size. I offer that service here in west Michigan. They pay for an oil change and I get to go along for the ride.

No. I've heard success stories and reports of boats loosing speed, can't get on plane, or other ill effects.

Mine got on plane with the prop shaft at 2 inches above the bottom. I am running a -3 IMCO shorty and installed an IMCO neutral extension box and raised it one more inch from last year. I was quite surprised that it got up on plane at all.

I think it all depends on the boat as well. I was told there was no gain going with then on my 33 zx