Any downsides tp flipping the axles?

Shock mounts may need repositioned on the frame or use longer shocks. Perch should be welded, IMHO. May need to add another step, extend the stabilizers and the brake wiring. Stabilizers become less stable the taller you go. Tongue height at the hitch will increase the same amount as the frame. Axle clearance does not change unless you put larger tires on.

It's easy to do if you have a welder & tools. I don't know if stability changes on a regular trailer. I've done it on 5th wheel campers & mostly because the trucks seem to get taller every year.