Murat is right, buy the Master America when the teak version comes out
All joking aside, I've been waiting to try one of the new rails too but we don't have them in the US yet. I have a similar one I put on my T-20 Mimetic open muzzle and to be honest I can't tell the difference in accuracy. Neither could I tell the difference in accuracy with a stock 100cm closed muzzle T-20 and an open muzzle T-20 Mimetic 100. I used the T-20 open muzzle for the first time during a competition in Florida and must have shot it 30 times and equally stoned as many fish as I feel I would have stoned with the other. Again, this is my opinion but I wouldn't throw this out there if I hadn't tried it myself.
Where the difference really lies in long guns with rails is over 110cm. With two bands it's good to have a guide for the shaft to come out strait without vibrations caused from the added power.
All Euro-tube rear handle-guns regardless of brand or construction are not balanced perfectly for two bands, the fact that the handle alignment is very close to the horizontal axis of the spearshaft makes them still accurate even with the recoil. The only way to properly balance these guns for two bands is by making wooden or carbon fiber or similarly unconventionally shaped elliptical ballasted barrels as Murat mentioned.
Ciao, Mark