Pumpkin/Fall Spice Ale - First time mashing with pumpkin/squash

So I'm putting together a "pumpkin" beer for the upcoming months and I'm looking for any comments.

Grains/Sugars:
8lbs - Maris Otter
4lbs - Butternut Squash in the mash
2lbs - Rahr 6-row
.5lb - Victory
.5lb - Crystal 80
.5lb - Crystal 40
.25lb - Special Roast
.5lb - Rice Hulls

Hops:
1oz - Kent Goldings at 60
1oz - Kent Goldings at 30

Spices:
1tsp - Penzys Pumpkin Pie Spice at 1min
1/2 - Cinnamon Stick at 1min

Yeast:
London ESB or something of the like.

Really looking for some advice in regards to mashing with this squash. I'm using squash instead of pumpkin because they're similar in flavor, but the butternut squash is a little more bold and a little less mess than pumpkin pulp. I'm planning on carmelizing it in the oven beforehand, but is there anything else I need to be aware of? Any other pointers are also very welcome. Thanks guys.

i just made one today. here i had a hard time with the mash. I expected pumpkin to contribute 28% of my bill, but it just didn't convert well. I fixed it to 1.060 from 1.048. it smells great, but just thought I'd let you know about this issue

I think you've pretty much nailed it.

Make sure you overdo, rather than underdo, the amount of rice hulls.

Underdo (as I think you've done) pumpkin pie spice. You can always add to finished beer if you think it lacks these qualities.

I think you have a cracker on your hands.

yeah i'm going to add more spice to the secondary. it tasted weak at pitching, but noticeable

It's worth mentioning that Pumpkin really doesn't contribute ANY gravity points. I'm not sure where this thought came from, since it's not a grain, and barely has any sugar whatsoever.