Belgian Specialty Ale IBU?

I am planning to brew a high gravity (1.100 O/G) Belgian Specialty Ale and ran the recipe through the Tasty Brew calculator. I was thinking that with that high gravity I needed an IBU around 60-70 to keep the beer from being sweet. All of my calculations are within the parameters of the style except IBU, which is listed as 20-40. Here's a synopsis of the recipe:
2 lbs various steeping grains
9 lbs amber LME (60 min(
3 lbs light LME (late addition-15 min)
2 lbs Belgin Dark Candi sugar (5 min)

Any input or suggestions are appreciated.

2 lbs is a lot of steeping grains.

I'd go 25% simple sugar (plain table sugar) and not use the candi sugar. 25% in 5 gallons of 1.100 is a little shy of 3 lbs. The sugar will help dry it out.

I'd just stick to light extract. You haven't really given us enough information to tell what style of beer you are brewing; a BGS, a BDS, or other. I'm assuming a BGS.

IBUs, you might push it to 50 IBUs. I just checked my notes and both my Chimay White and Duvel clone were around 35 IBUs for a 1.070 beer.

What yeast. Get one that attenuates well.

Most of my Belgians range from 20-30IBU's. The St Bernardus is 1.103 with 13 IBU (4# of sugar though).