Even without symptoms of pushrod flex (begins with tiny scratches or polishing of the tube by the relief hole sides about mid-way), the extreme deck height of the 292 suggest using the largest OD that clears. Adding length greatly reduces stiffness. Top names (Trend, Smith, Manton) can tell you.
OD is far & away more important than wall thickness, even an extra 1/16" is worth having.
A theoretical example, using .100" wall to remove a variable, and changing only OD.
Going up from 5/16" to 3/8" OD more than doubles bending resistance. The weight increase for 10" tube length is about 25 grams each, or 30% more.
