Thx.
Got the full hole cut and replaced the cement blocks it was sitting on with some temporary big wheels. Kinda looks like one of those street food carts in the short term. At least I can move it around now, and get underneath better to work on it.
I had been using a piece of table glass as a template for the hole, with packing tape around the outside so it wouldn't shatter... worked pretty darn nice, if I do say so, although it did crack once it fell through after cutting. It was cool being able to see through it and that it was still all lined up while cutting. Now to decide which part to work on first... so many options here...