No advice on the grain bill, but that's a cool pumpkin.
I also thought this year's pumpkin smelled great while carving it.
The general consensus is that pumpkin doesn't add much, if any, flavor to a beer. It may be that the flavors are driven off during the boil or simply not strong enough to compete with the hops and grain. But I don't think that you should let that stop you.
I think, though, that the amount of hops in an IPA might mask any pumpkin flavors you get.