We probably can slap drop tanks on a .91 floater & with a pair of good binoculars fly around at FL181 all day... cause we are not regulated by Tital 14 of the CFRs.

or does that seem just plain illegal incursion to controlled airspace?
Being a recreational model doesnt let you just pop above FL180 at your liesure, the feds (FAA) will come knocking and not in the "We brought you a fruit basket" way.

If you want to call the FAA to get blessings,
tell them you are gonna break ClassA in 20mins and they cant do anything to stop you, and then give them the field you are at address. Remind them they dont regulate models, so the ClassA regulations in CFR T14 cant apply to you, I'm sure they will love the irony.

Go ahead, We'll wait.
Call the tthe FAA & threaten to break FL180, and see if they say they dont care what you do with your toys.