I wonder if adding 2 fuel pumps would help… assuming they don’t already have them. The standard float needle (at least the ones I’m familiar with) in small Honda carbs will handle 4.5 to 5 psi easily ( stock) and higher if necessary. I have a couple of Ducati vacuum operated fuel pumps in my “ some day I might use that” pile in the shed. No idea what sort of volume they will push. They are small and light, but the vacuum part might be an issue?