one inch on 16" prop isn't a lot

the radials used on the old WW2 planes were a compromise -just like airfoils - it is all a compromise and they used huge props to make it all work
on our little IC engines, the big props simply are too big to allow the engine to run in the power band
latr on - the benifit of moving the props as far forward the cowl as practical - and blending the spinner to the cowl - improved things
Personally I try to get the prop as far from the cowl as possible -on any model --