[Dave]

Well... we went for a sorta bulldozer/rampdom bot this year... two 4 foot arms protrude from our robot's sides... made out of a single piece of 1x1 extruded aluminum (!) Noo.... it won't break.... we've been using the pieces to pick the robot up AND whale on some metal with... They've got these cool little cross-pieces which make it look like an x-wing...
Our bot weighs about 130 lbs... it's doing well.
It takes about 700N to twist our bot with NO compensation from the drivetrain... YAY!
Oh... and if you can move your walls (retract, raise, what have you) then you have complete control over the field... you can still go block the sides if it's that much of a problem.
And swinging piece of metal is great at hitting those nice, tall stacks.
SPIN LIKE A WHIRLING DERVISH!