Yeah, you are right. I thought of that after the fact. The bottom one is actually a 2x8, sufficient width to bridge the two forks, but the upper 2x4 would be better on edge.next time( yeah, there WILL be one....) mount the 2by boards 'on edge'. They'll be stronger, won't flex.
Too late. It's welded up solid now. I was striving for maximum stability. I forgot to include this picture:I found with a front mounted boom pole, it can be handy to be able to use the boom in different places (ie attached to the left or right for better/tighter access etc - I was setting trusses with mine). Suggestion: maybe put a couple more pockets for the pole on your SSQA mount in addition to the centre one?