Do it now.
You install the gear while the 'boat' is upside down, then you turn it over and finish tightening up all those little nuts that are too close to the edges of the angles and weldements. PITA! After it is on the gear you can roll it around the shop, or out into the yard so you can clean the shop. It's not too high to work on the canopy. A short ladder, step stool or part of a Van's crate will get you inside or high enough for everything else.
The windshield and canopy go on after. Remember, the fuse gets heavier as you add stuff to it, and turning it over would geat harder, as well as risk damage to the windshield.