Woody's Signature Series SS Stud with the Tall/Big nuts is what I have been using for years with GREAT results. I'm just your average trail rider and don't pound the heck outta the sled. Make sure to use Woody's backers too. Can't help you with a # of studs but Woody's site has a great tool for determining the right number of studs.
http://www.woodystraction.com/home
I just went there and put your sled through the selector. If you select "intermediate" riding it will suggest to run studs on the outside belts. I've done this 1X and will never do it again. Good luck which ever route you choose!