Based on the results, you have to conclude that extra output is being developed. What, exactly, is going on, is more difficult to determine without a cylinder pressure measurement and records to compare.
Something to keep in mind is that air cooled engines (is this air cooled?) typically run hotter chamber temps, and this assists in fuel vaporization. BUT, some engines (and some fuels) do NOT like vaporized fuel. Yeah, I know that in theory, complete vaporization SHOULD produce more bhp, BUT, some engines (and fuels) simply produce more bhp when the fuel "rains in" in larger "droplets". How do you know what works better for you? Testing and documentation is the only way. Race tracks can substitute for dynamometers if you can data log . . . . . . although the changing conditions of the track or the weather can drive a person batty.
Most "Cosworth" designs function very well with .41"/.44" gross cam lift, and you are not very far from that. The Cosworth cam designs, do however, run "lots" of duration, usually not a fitment problem with 4 valve engines. BUT, yours may be "unique" depending on the Build Geometry. A "high" rod length/stroke ratio may hamper flow demand and room for valve clearance @ overlap. At least you should be rid of the 2 valve hemi valve to valve clearance problem.
The compression ratios can be "modest" with "flat-top" style pistons, depending on displacement per cylinder. You might want to do a very accurate measurement and calculation of your actual C/R, you might be surprised. If you do the measurements, I'll run it through my copy of Compression Ratio Calculator Pro. Be prepared to measure a few things not normally checked. Modest "intruder" style pistons can gain some output via higher C/R, at the cost of increased component stress . . . . . .
Keep in mind that there are ALWAYS compromises for fitment, or to utilize existing bits, etc, etc, etc.
The "trick" is to make the best choices out of the options available. Informed decision making ALWAYS works out better in the long run. There is never a short run, because measurement and analysis takes time, adding to the length of the build. AND, analysis can make you regretful of parts choices that were guesses.
Fordboy