Has anybody had any first hand experience good or bad with the Imco 2" shorter lower units for Bravos in the less than 70mph category

It's borderline for your requirements, but a shortened lower and a reprop took my old boat from 69 to 74.

what was your boat and hp.

a good question, I am thinking on going two inch shorter on the drives and add a pair of labbed props, easy speed, and its reliable

I have for sale a set of imco 2 inch shorties with xr shafts for sale. These are perfect, $5000.00 for the set. I had them on my Daytona but am selling the boat and my new boat has #6 drives so I can no longer use them. Doug

It was a 24' Concord LS-7. It had a 454 W/365 hp. The boat was a real handful to drive. It was a loose ride that took alot of concentration to keep from chine walking. This was due to the large amount of trim the boat required and the shortened lower.

http://www.concordboats.com/ls710.htm