That's the nice thing about going with non-NRS, They can be cut... I ended up buying just the cast oar mount pieces from AAA and put them in some 1 1/4" tubing, then attached to the frame with Lo-pro's. I made several lengths with cuttoff's from past frame projects and currently like mine about 9" above the tube... I'm pretty sure the OP is planning/talking about NRS towers, but you might consider one of the other brands...
With that said I saw a pair of the new forged towers over the weekend and they are purdy!!