I’d start with superglue, also @pixeltree@lemmy.blahaj.zone makes a very good point. Creating some aligned holes and pins would make the assembly much more exact. I did something like this when I edited this model to fit on my previous printer. Slice the model and while it’s aligned in whatever editor you are using, create a 3mm diameter pocket which goes 5mm deep in each side in three places, creating a triangle of pockets. Then print some pins which just fit those holes. This will ensure everything lines up nicely. Once printed and glued, you can use a filler putty like Bondo to fill any gaps. Then sand and paint.