Antonio,
The advantage to hollow ground is not in slicing. Although, for deep slicing, hollow ground knives actually work to wedge open the flesh and break surface tension to make deep cuts easier.
The real advantage is the leading edge cross section of a hollow grind will be thinner for years longer during normal use than a flat ground knife. That's because the more a flat ground knife is sharpened the thicker the cross section of the leading edge gets. Hollow grinds stay thinner longer.
That's also why well made kitchen knives that are flat ground are usually thinner in cross section than a sporting design of a similar size. To keep the leading edge cross section smaller.
A flat grind's greatest value for a sporting knife is in its strength when the edge is subjected to lateral loads through chopping or throwing...that sort of thing. Although that advantage is marginal.
All grinds are intended for and have advantages and disadvantages for specific jobs. Knife makers usually just do what they like or a customer wants cause they think it's cool. ;~)
Keith,
Yep, practice is what it takes. And TONS of patients. LOL
If you look at a lot of the better folding knives, which do have smaller blades than typical fixed blades, they usually use an 8 or 10 wheel and put a shallow hollow on them.
As H. L. says, the size is about what you are trying to get done with the design and personal preference. I actually like a 6 inch wheel for most all of my designs. I just like the way the deeper grind and wider spine looks and works for skinning knives.
I think the most important thing is to have a clear vision of what you want the finished grind to look like, lay it out on the blade and follow the vision.
But don't to hung up on getting it perfect or worry about it if it doesn't go exactly as you intended. Final sanding will fix WAY more stuff than you might think. Trust me on that one. LOL
Stick with it man. It's just takes practice.