I think that's about what my deck height is too. If your RS is anything lower than stock height it might be tight even with those extenders. I use mine for RallyCross and run a tire that's about 1/4" taller than stock and my front lip has less than 1" clearance to the ramps on approach. If your tow vehicle has air suspension and a higher off-road type mode that can help in this regard too.
Another option is to look into longer ramps for the trailer itself. On mine the storage location goes up to the axle so the 5' is all I have. It's worth noting that the Race Ramps weigh nothing and there is room to store them underneath the back of the RS at the back side of the trailer on top of the deck.