you may well!! all depends on the height of the trailer hitch
is it a twin axael trailer, when i towed with mine dropped 60mm with a single axel on a small boat trailer it was ok (the jocky wheel did botoom out but only a couple of times)
but when i towed a heavy duty twin axel box, the rear trailer wheels werent even touching the ground!
In short coupled with that and ride quality and clearance for some lanes etc i have gone back up to 40mm drop.
Also note what are the springs rated to if they are not heavy duty and the trailer weighs a bit it is going to go down even further, and if you tail load the trailer too much its asking for trouble like upside down van!!
lowered 60mm mate,tow all the time with a large trailer and velle's on the back,brings the van down abit,but nether had a prob....the jockey wheels can be removed from the trailer by jacking up front of trailer and un winding wheel from top,bottom drops out.
just make sure you even out the load on the trailer,so the van sits straight and trailer is sat straight,moving car forwards or backwards on trailer will give you the best position.....and strap that car down well.
im lowered 60mm and going to go back up to 40mm as i tow a front heavy trailer,never rubs tyres but its low-i can put 4 fingers between towbar and the ground,infact the trailer caught the ground when we were entering a field in 1st gear and bent my towbar,good job we were wearing seatbelts as we nearly went thru the screen H: