Letus makes a longer riser to use with the barrel up position, you just rotate the gg barrel so the screw hole is pointing down in the barrel up config.
I've got mine mounted this way and it's as solid as barrel down. With the extended riser now, I've got two rail mounts and can mount a higher set of rails for ff / mattebox. Prior to this I had MacGyvered a solution using Brevis rail mounts. Only problem is in that config, I couldn't get the Letus to mount via screw to the rails so I much prefer this new set up and it's cheaper.
