Procomp set up

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.

I used to run OMC loopers on my procomp.so they were a bit heavy too...I ran 4" setback ...Prop shaft around 1" above pad...had dozens of props for it , but the merc lab cleavers were my go to props for the most part...they also were the fastest up top and felt best at speed to me..mine had the ski bottom ..trapped a lot of air, and with a heavy motor got light with bow lifters..

Most of the guys running 3L STVs are running 4 blade overhubs. They seem to give the extra lift that it takes until the case is surfaced and supports itself, the boats seem to be planted. I personally like the Dewald or Herring four blade but they are pricey so I run a Mercury Pro-Et most of the time. They are 10 to 15 mph slower on top end but carry weight well and make a great river prop.

I would always recommend that you get the larger dia. prop shaft and billet carrier if possible. Pro-comps are still very cool in my book "tons of great memories".

Joe