My previous 19ft TT had very low ground clearance. Its plumbing discharge pipes was in the rear and many times, I seen grass strands hanging off its rear plumbing pipes. Thus, waiting for an accident (re: smashing its rear pipes) off the bottom of the TT. Thus, I re-positioned its axles "under" its factory leaf springs - which created 4.5" mpre ground clearance. For my situation, re-positioning its axles was well worth it. Glad I did it.
The buddy across the road pulls an older 5er. In the old days, the bed of pickups were much lower (compared to today's pickups). To reduce the risk of the front of his 5er scrapping the top of his pickup box, he re-positioned its axles under its leaf springs as well. Thus, more clearance from its higher height box. Especially during uneven camp ground areas.
In both cases, handling around corners and wind drag was NO difference. I certainly couldn't feel a difference...
For more details, surf: http://www.rverscorner.com/articles/axles1.html
Depending on the situation, re-positioning axles under the leaf springs are worth it...