C2,
I see what you are thinking - have to be stationary for the make a pile feature. No, none of the islands would work, after a short while the serps would spawn far enough away that you would not be able to target them. I am not aware of anywhere that they spawn consistently enough. If you have two toons on that little island off of Bucs I bet you could cover the entire thing and keep it going, but I would guess it might not be as efficient as a single toon at a better spawn location.
I think OMG's plan might work in some Lost Lands spots. Good chance you get smoked before you finish though.
I am intrigued by the Sak Teb location in Lost Lands Fel.
http://uo.stratics.com/database/view.php?db_content=atlas&id=1337 It looks like it has a good mix of spined leather creatures with only a few other distrations. Might be worth going to scout to see if there is a spot that you could beat on. Giant Toads and Alligators give 24 in Fel.
For gathering spined leather I currently use a modified version of Jebbits Leather and Bone recall script. I set it up to target alligators, giant serpents and wisps and have it rotate through the tropical islands. It does a solid job of keeping me in spined leather and bone and I have only run into one or two PKs in a couple of years of doing it. Seems no one else is on to my plan on my shard. I have it pick up the gold too. Happy to share my mods with you if you are interested.
-P