The DW hoop clamp has a lightly padded inside & grips the edge of the hoop. I use the hoop-mounted spurs (same clamp piece), and have no trouble with scratches or any kind- though for right now I'm using a cymbal stand-mounted tom arm for my cowbell.
Thanks very much.
Question 2 - what's the best cowbell?
Haha
whatever Charlie Watts used on Honky Tonk Woman - you can use on everything
Moooo
Yes I have a tama one that mounts to a cymbal stand but it just doesn't reach far enough to be useful anywhere other than under the hats (not a fan). My cowbell is an LP matador wrapped in gaffer tape, I think I like the bigger lower pitched ones.
(By the by, the Meinl hand-hammereds also come in two different colors and 6.5" or 8" size.)