Just took apart a set of 74, 34mm forks yesterday, had no trouble getting the caps out, though it was obvious that someone had at some point.
I have a universal axle tool for sport bikes that has stepped sized hexes from 17mm up for the various axles that utilize this type. It worked like a charm.
The caps have a thick rubber o-ring seal so turning them just till they're snug is ample as the o-ring with prevent them from screwing themselves out.
Had to cut off a 8mm Allen key though to use in a sock with my palm impact though to get the bottom screw to spin out. It loosened fine but just spun after that. A little high rpm and it spun out perfectly.