That's a good idea...might really work well.
And if there is no room for the Allen wrench to fit in the end, cut the main shank to the correct length and then drill a hole through the side so you can poke a straight piece of rod (or the straight end of an Allen wrench) through to provide the turning lever.
If you measure the necessary length and cut appropriately, there will definitely be room in the end for a 5/16" Allen Wrench to fit in one end, the other on the truss rod nut... The only reason I haven't made one up like this yet is, the standard Gibson wrench works on all mine - if it didn't, I'd be breaking out the cutoff wheel, lol...
