Thanks for the link, but, unfortunately there were no brakes in that link that I could find with ports venting rearward. I do think that the Holland brake, if the vents were angled rearward would work well.
I am aware of the Armalite AR-30 brake, which is an option I am considering but would prefer one that is like the Serbu BFG brake but downsized to fit smaller diameter muzzles on 338 tubes. Based on my own experience, the BFG Shark brake is as close to perfect as you can get on a 50 BMG. Substancially less gas in the face of the shooter than the Armalite but only slightly less efficient in recoil reduction.
I am not even remotely interested in any brakes that vent at 90 degrees, as all they do is cancel out the thrust from the gas venting forward. They don't utilize the jetting gas force to further reduce felt recoil by counteracting the rearward movement of the rifle.
I am frankly perplexed by the thought process that goes into making a brake that vents the gasses to the front. That type of venting is in fact counterproductive, actually adding to the felt recoil / rearward movement of the rifle.
I have talked briefly with Mark Serbu about producing some scaled down versions of his Shark Brake. If anyone is interested in getting one, let me know. It will be a long wait I am sure, he is a busy man.