I used Quickfist clamps with a shovel and Axe on a Surco for a good while, never had any problem..
Had to do a little bit of modifying to get it right though..
Notcie the extra metal strap..?? You can find it at Lowes or Home Depot for not much dough.. Shoot it black with Krylon Textured Finish and bolt it on.. Mounted the Quickfists to it with a nut and bolt setup. Simple.. The front fist had to have a standoff between it and the strap on the rack to give clearance for the spade end of the shovel. I used an old socket shot with the Krylon.. Quickfist were mounted to the inside of the rack rather than the outside.
This is the best picture of the set up I could find.. Got rid of the rack for somethig a bit stronger about a year ago.. Have to fiddle around to find the right placement for the shovel..
Didn't leave the stuff up there ALL the time, but when out on trips it was always up there and as far as I know they were never messed with..