I take my hat off to you for doing your own fab work.
As a guy that has work with fabrication of steel and ali for over 20+ years I have found that it does take a guy with a good healthy set of “tools” to back himself and just go for it.
As for Charles’s love of fluid, cutting fluid/coolant I mean. He is spot on, it's a must. Even if its just water in a spray bottle, sprayed at the cutting tip every few seconds it will extend the life of your cutting bit and give you a cleaner cut.

Best of luck, back yourself and go hard at it (after you have measured twice)

Keep us posted with lots of pic’s