The other solution instead of a roll bar might be a wing. I haven't beaten on this wing seriously yet so I don't know how well it stands up but the combination of the wheelie bar, wing and metal plate stiffening the rear shock tower I think my esc might be OK. Also mounting the shocks on the front of the rear shock tower helps stop the tower flexing inwards.

http://lh3.ggpht.com/MTBikerTim/SBQs...JPG?imgmax=640

I still would like to get the roll bar on but it's not going to happen until I get a new servo and a metal servo horn.