I did something similar on my 21' in the first 1000 miles. I used a 6" diamond blade hole saw. I am running the Jowett Filter housing & ez drain valve on the pan.
That looks very clean. I like it. I think I would go a little less than 6" since I don't have the jwoett (sp?) Valve and only need vertical access. My 3D printed hole cap may be fully unnecessary, but I will probably make it just for the practice.
if you just go with the front, engine & transmission plates mount up to stock bolt holes. the 1/4" aluminum offers a lot more protection than stockDo you know if it bolts in to the stock locations?
Also, any clue if the rest of the panels work with this system. It's my wife's (for now) and I really don't want to alter the look.