first off, it sounds like adding a tower would void your hull warranty if you have any left. so if you're OK w/that -
it's a nasty job, but you have to build up the 'glass on the underside in the mount areas to about 1/2" thick, in as large an area as possible around the mount. you may also 'glass in metal backing plates, but
DO NOT IGNORE THE DEALER'S ADVICE here's an example of a Skyjac universal on a 2000 Capri 2050:
http://skyjac.com/Boat_Tower_2001_small.jpg email me offline for excellent pricing on Skyjac products.}