Within the past month, I completed an over-slung axle conversion (re-located axle under the leaf spring as opposed to over as it was OEM, on my 89' Layton.
Check under your rig and look at where the axles are located, are they under the leaf spring (over slung) or does the leaf spring go under the axles? (under slung).
If your currently under-slung as my Layton was, then you can do the re-location. I gained at least 4" of ground clearance doing this and I would never go back to under-slung again. My sewage pipe connection and valves are behing the LR wheel so when my rig was under-slung I had literally 6" MAYBE of groung clearance and the prior owner's installed "steel wheels" on the back hit when I backed into the driveway for the first time at my house (bad can twist the frame)
Now, the hitch the prior owner gave me did not have enough drop on the shank, so I was towing nose-high, however I don't think an extended drop shank, and getting the trailer dead-level hitched up would have allowed me to back into the driveway and still not hit those wheels.
So I figured I'd wack two birds with one stone, do the axle re-location, gain ground clearance (the 89 Layton from the factory was a REAL low-rider which I didn't like) and then I Could retain my existing hitch shank.
I spent about $120.00 for the two dexter axle relocation kits (one kit does one axle) and probably 4-5 hours of time. This was the first one I ever attempted, so if I was to do it again I could do it in probably half the time)
Towing wise, I didn't notice any difference at all, under slung compared to the re-located over slung set-up. I will say this, I have been spinning wrenches for 23+ years on a variety of equipment from heavy truck all the way to ATV's, go-karts, ETC. If you don't have a good mechanical background I would take it somewhere to have the re-location done. Getting the rig jacked and properly blocked is VERY important. I reccomend hitching it up to your tow vehcile before jacking so the front is anchored. I also used a long-frame floor jack from Harbor Freight when I lifted the camper, as my standard floor jack did not have enough lift (ram) to get it high enough.
Make sure you have the tools, equipment, safe place to work an experience if you attempt this. It's not worth your life, or loss of limbs to save a few hundred dollars if you don't have what you need to do this type of work. It's not super-difficult, but when your dealing with weights such as your trailer, it's nothing to fool around with. This is my .02 for what it's worth.
I was suprised to see my brother in law's 2006 Keystone Outback 21 came from Keystone under-slung. Yet, his rig seems to have a lot more ground clearance even under-slung than my Layton did. His has 2 entry steps as well which confirms this (the layton only has one so I just put a small stool on the ground for the first step).
Another good idea on his Keystone I like is that the sewage connection is FORWARD of the LF tire and not behind the rear one. There is MUCH less chance of it getting hung on something where his is.
The only odd thing I've found about his rig is that the water heater only has one valve to put it in bypass, which does not make sense to me (mine has two one on the inlet and the other on the outlet), but I suppose a lot of other rigs are like that and it must bypass it somehow?
Good luck in your decision.
-Greg
2017 Dodge Ram 2500 HD, 4x4, CCSB, 6.4L HEMI, Snow Chief, tow package.,1989 Skyline Layton model 75-2251.