I'll make sure I use a decent size pot.All good as long as you go with a big pot (5 gal min) I would also make it a cloth pot. Autoflowers react badly to getting root bound, they'll flower early and you could end up with a three gram plant.
If you can spare the seed I'd try a heat of the summer grow ... I grow indoors at temps up to 37c and plants prefer outdoors ... can you plant one in the ground in full sunlight that can grow to over 100cm ? If you can give it full sunlight you can always shade it on extra hot days ... Do you need to hide it ? Can you keep it watered ? Do you have access to nutes ? You appear to have a green thumb which always helps ...
My last high temp grow ... https://www.autoflower.org/threads/high-temps-nlbb-bubblelicious.45970/page-17#post-883979
While she looks to be a pretty nice plant for some reason she never fully committed to flowering ... it could be she will pack on some more buds in the next couple weeks ... how much direct sunlight can you get it in a pot outdoors ... a Mars 48 sounds sorta weak for flowering ...
In your backyard would that be 6-8 hrs of sun and the rest heavy shade or filtered sunlight ? If you planted it in the backyard and it grew to 2m could you leave it there for the whole 3 months ?
the more direct light the shorter the plant ...