I have had a few twin tunnels and now have purchased a 1991 Procomp with no power. Installed a rebuilt 1993 Yamaha 250 HPDI with a stage 3 kit lifted the compression a bit. Flashed he computer. With 6" set back manual jack plate. Getting ready to send off the lower to HT for low water drilling and some reshaping. Since the procomp needs to run above pad an inch or so do I need to run a fat shaft as well? Also the Yamaha is heaver than Merc 2.5 by over 100lb what type of prop should I be using? I have a lab 28p 4 blade Merc bravo will this have to much lift? Please let me know what you think.