For a softie tank,I'd go ahead and do the internal DSB.When you aquasape,dont put the LR in the sand.You can make stands/supports with PVC to keep it off of the SB.By
drilling holes in the LR,you can use PVC as dowells to make a sort of tripod that will support them.You can also use them to connect larger pieces of LR together that will further strenghten the aquascape.The idea is to keep us much of the rock as possible off the SB thus allowing good circulation to take place at the sandbeds surface.This will also allow easier access for occasional siphoning.
When LR is placed in sand,it tends to accumulate detritus and clogs the pore structure of the LR.IME,these rocks are always the first in my DSB reef to get overrun with problematic algae.