It says inlet velocity/freestream velocity, or stream tube area/inlet area, are numerically a low ratios.
Velocity, on the other hand, varies a lot at different points in the system.
There are only two ways to carry away more heat. You must flow more mass or transfer more heat to the mass you have. Recall I asked about exit temperature? Yours is not very high, so if cooling is good, you must be doing it with mass flow. Think about it; you have a lot of deltaP.
High deltaP across the engine baffles also says flow through the fin passages is at high velocity, at least at some points.
I really want to see a data set before drawing a firm conclusion, but I'm beginning to think your extensive wrapping is too restrictive. We don't want the system restriction to be the engine baffles. We want it at the cowl exit.
Consider this tidbit from Hoerner's
Fluid-Dynamic Drag. The given values are for radiators, but something similar would be true for engine fin passages. I think the good doctor is saying that if velocity within the cooling passages is reduced, heat transfer won't fall near as much as drag, i.e. energy loss across the engine baffle. So, open the baffling a little, and clamp down on the exit; slow flow in the fins, maintain higher lower cowl pressure, and generate faster flow through the exit.