I have the same problem. I have only tried 3 full hollows, but the "more hollow" ground ones cut better for me. The 5/8 "bordering on extra hollow" cut easier for me than the 6/8 "legitimate full hollow", which cut easier than the 5/8 "almost full hollow".
ps: I find the gullotine technique works really well to get the cutting started under my lower lip and on my chin where the hair is particularily coarse (and also on my upper lip if I skip a day shaving). If I come straight down in those areas, I have to press pretty hard no matter whether the spine is .5, 1, 1.5, or 2 spine widths away from my face.
See: Shaving passes - Straight Razor Place Wiki