I too added about an inch spacer to the rear of my truck to make it sit level with no load. Added air bags to the rear so it sit level with the weight of the RV. (dropped about 2" when loaded).
When both units were level I only had 2 1/2" clearance from the top of the bed rail to the bottom of the 5th wheel. I made 2"x2"x 4.5" steel pinned spacer blocks for the RV's axle to raise the unit, I also bought taller wheels and tires. Took some work but now both RV and truck are level and a proper bed rail clearance. This is just a guess but I'm thinking your Sundance's nose will be 5"-6" high when hitched up. If you decide to correct this just let me know, I have longer axle u-bolts in stock and can make blocks any height you want to raise the rear of your coach.