2007 Sportman has a rack with many holes and metal "sleeves" - how can I install a seat with U bolts on this?

 

Couldn't tell you about how to mount a "generic" back seat or back rest,but the lock and ride options could give you an idea.Polaris Backrest: Parts & Accessories | eBay

 

I installed a Wes Industries rear seat/box on my 2001 AC 500. Was very easy,need a cordless drill with 1/4" drill bit and a 7/16" socket/ wrench. Have someone help you hold it centered while you drill for u-bolts. Bit of a PITA to get the u-bolts up thru, might need someone with small hands. If you ride 2- up on a regular wheel base ATV, be very careful. Going up hill, you can flip backwards easily. Also realize you have a lot of weight, with 2 people, above center of gravity. I use my ATV's to post bear hunters to stands, so, I now have 2 AC TRV, long wheel base machines. Much better with 2 fat guys on board, hehe.

 

I have a Polaris Lock and Ride backrest on my Sportsman and it's a lot higher quality than the generic one I used to have. The metal is all heavy duty steel instead of flimsy aluminum. It's also easy to adjust forward and back by loosening 2 *****. My old generic backrest wasn't adjustable at all. Take a look at them before you decide what to buy.