[Ed]

Redrum-

If I were you, I would make the main cuts where you see fit than I would grind back 8 inches on either side of the entire main cut on the "outside" of the pilothouse. Next, on the "inside" of the pilothouse I would take a circular saw or something similar and set depth of blade to just shy of the thickness of the core...(maybe 3/4 of an inch. Not too deep because you dont want to cut all the way through!) I would then, using the circular saw, make a cut line 4 inches all the way around above the "main cuts" and then again 4 inches all the way around the bottom of the "main cuts".

Then I would remove the 8 inches of core between the two cuts. Next, I would get some 2x4's and bolts and I would temporarily bolt the cut sections of the pilot house back in place with the 2 x 4's and make sure it is plumb and level before you start glassing.

Once you are okay with the layout, I would get some core that matches the original (again, maybe 3/4 inch ply?) and I would cut it to size (taking into account how many inches you extended up and aft). Once the plywood is cut, dry fit a couple of times to make sure it fits 100%. Once you are okay with the fit, mix up some epoxy with cabosil and trowel it onto the inside section of the pilothouse where you removed the core. Next, press in place the core and clamp or bolt it down until the epoxy cures.

Once it has cured, cut yourself some 1.5 oz mat that is slightly bigger than the new core section (maybe 3 inches larger all the way around) and lay it up on the inside. Follow this with a piece of 1808 biaxial that is 4-5- inches larger than the core and lay it up on the inside as well. Finally, follow up with another piece of 1.5 oz mat that is 6 inches larger than the core. This should take care of the inside for now.

Next, move to the outside and follow the same layup schedule. (Depending on where/how your temporary 2x4 staging is setup...you might have to swap it over to the inside so you can now work on the outside.)

The only thing that is hard to say for sure is the actual number of layers of glass you'll need. It all depends on how much glass the factory used originally to make the pilot house. If you use too much glass to piece the pilot house back together you will be grinding forever...if you use too little, it wont be very strong and you will be putting on a lot of epoxy fairing compound to raise up the height.

Again, this is pretty complicated to explain over the net, but I am sure you get the picture. Also, I am sure Bobby (WARTHOG) will have some specific suggestions too. The guy built his own pilothouse on his 23 Mako.

Good luck and take your time and measure 3x before you cut anything!

Ed