Its more than enough surface area and bracing to support your seat. In fact, with a closed loop, the cross bracing is superfluous. To Sean's point, you may actually want to remove the flat stock to allow the tire to move upwards during suspension compression so as not to conflict with the brace/tread.
You are not the first to perform this modification and not realize the potential for conflict. Nor will you be the last. Longer shocks tend to be the requirement afterwards which alters the steering geometry and thus, the negative feedback from some with prior experience. Don't take slightly snarky comments personally, its just that certain "mistakes" are seen repeatedly and some folks get tired of explaining the same thing over and again.