olieboy - looks like a great idea- wouldn't matter what the bench material was.
Just noticed and wondered why your postion is so loose? By loose, I mean unstable - if you rested your right elbows and left arm on the table(sitting closer to the cuttout of the bench) your accuracy should improve quite measurably. I do see the problem with the bench not being long enough to rest near the muzzle, but I'd found when bench rested, most longrifles (yes, long ones too) shoot most accurately if rested just back of the entry pipe on the wooden forend, and with a bit of padding to absort vibrations. However, if that's your style, that's just fine.