Well, I used Plumber's GOOP to seal the block, but that was a VERY BAD idea
The GOOP's fumes caused cracks "sunbursting" around every single drilled hole in the plexi. Nothing was tightened down fully yet, and it cracked on the yet non-used P4 holes, so it wasn't due to me over-tightening anything.
It was a prototype, but it still sucks. I cleaned the GOOP from the barbs and put them back in sealed with Weld-On #16 (thicker) to try to seal the cracks. So far, it doesn't leak with full-on house tap water flowing through it, but the cracks are slowly getting bigger.
Since I might have to junk the top, I added a little "flare" for the hell of it... (with some internal condensation from the leak testing)
