Difference between a 99 IS and a 00 IS seat

[NighthawkVTX]

I recently picked up a 2000 IS seat to replace my 99 IS seat.
The thing is, I can't get the new seat to push all the way back into the rear.
The seat will lock in, but there appears to be a notable gap. I can see under the backrest unlike my original seat.
Is there a subtle difference in the two years seatis

[Jess from VA]

All Interstate seats should be identical. 

Have you turned them over side by side to compare?

Is something bent?

[Mooskee]

I had an IS fender I put on a Tourer. My problem was the opposite of yours. When I went to mount the Mustang tourer seat it would not go on. I looked at the fender lug that the back of the seat goes into and there was a welded on piece of round bar stock about 1/4 in diameter. It was part of the lug and was painted. I took a cutoff wheel and a side grinder and made the seat fit. I just went on ebay and looked at pictures of rear fenders. some have the bar stock on the lug and some don't, however there didn't seem to be any rhyme or reason as to which were which. You can probably get someone to tack weld you a piece of round bar stock on there though. If done on the bike safeguard your ignition system.

[gordonv]

I will say all the IS seat pans are the same. You do have an one piece IS seat, and not an aftermarket 2 piece or a Std/Tourer seat, right?

You should be able to just flip them both over and compare.

I never had my IS seat installed properly, but it latched and held in place. It wasn't until I had help working on my bike at our annual Rally, that someone pointed out that I wasn't getting the 2 front "tabs"/hooks pushed into the frame (its been a while, I hope I have that right).

But the IS 2000-01' seat supposedly is more comfortable than the 99'. So they are different, but interchangeable.