It fits!

I did a test fit with the new holding tank and it fits.  I need to make a support for the bottom of the tank and finish the new hatch but very happy with the progress to date. 

Once the support is in I'll screw in some hold downs at the front and back of the tank and also run a hatch support brace.  I'm waiting for some teak trim strips now - hope they arrive before the weekend so I can complete the new hatch.