Belgian Dark Stron Ale (Chimay Blue Inspired) - Is this too much sugar?

Hey,
Im planing on brewing a Belgian Dark Strong Ale and am curious if 10% candi sugar is too much.

Recipe for 6.25 gals:

Recipe Specifications
--------------------------
Boil Size: 9.39 gal
Post Boil Volume: 7.02 gal
Batch Size (fermenter): 6.25 gal
Estimated OG: 1.081 SG
Estimated FG: 1.012 SG
Estimated Alcohol: 9.1%
Estimated Color: 25.9 SRM
Estimated IBU: 25.2 IBUs
Brewhouse Efficiency: 70.00 %
Est Mash Efficiency: 76.5 %
Boil Time: 90 Minutes
Estimated Fermentation temp.: 71F

Ingredients:
------------
Amt Name Type # %/IBU

0.17 kg Special B Malt (180.0 SRM) Grain 4 2.0 %
0.17 kg AbbeyMalt (22.8 SRM) Grain 3 2.0 %
0.10 kg Caramunich I (Weyermann) (51.0 SRM) Grain 5 1.2 %
0.40 kg Wheat, Torrified (1.7 SRM) Grain 2 4.6 %
7.00 kg Pilsner (2 Row) Bel (2.0 SRM) Grain 1 80.6 %
0.15 kg Candi Sugar, Clear (rocks) (0.5 SRM) Sugar 7 1.7 %
0.70 kg Candi Sugar, Dark (rocks) (203.0 SRM) Sugar 6 8.1 %

20.00 g Galena [10.10 %] - Boil 90.0 min Hop 8 19.9 IBUs
30.00 g Hallertauer Hersbrucker [3.50 %] - Boil Hop 9 4.8 IBUs
20.00 g Hallertauer Hersbrucker [3.50 %] - Boil Hop 10 0.5 IBUs

2.0 pkg WLP500 Trappist Ale Yeast (Wyeast Labs #1214 equivalent) [1 Yeast 11 -
1.00 tsp Yeast Nutrient (Primary 3.0 days) Other 12 -


Also my planned mashing schedule:

15min rest @ 122F
60min rest @ 144
30min rest @ 156
no mashout, use boil to denature enzymes.

is this mashing good?

Recipe looks good. With simple sugars only making up just shy of 10% of your fermentables, you should be fine. I'm not sure if ~1.5 lbs of dark candi sugar is too much though, I can't say from experience if that amount will be overpowering or not, hopefully someone who's used it will chime in. From what I've read, Chimay actually just uses corn sugar for their simple sugars, and it only makes up roughly 5% of fermentables. That said, a lot of Belgian brewers use between 15-20% sugar with no ill effect.

If you want my input, I would drop the dark candi sugar down to leaving you an SRM of around 20 or so, and replace the amount taken out, along with the clear candi sugar, with table sugar. That's just me though, whatever you do with your recipe is your call.

10% candi sugar is definitely not "too much". I recently made a BDSA with a little over 20% of the fermentables coming from sugar (that was 3 lbs. of 180 SRM sugar for me) and it tastes quite good. You should check out this thread. Saq and others did some hard work and they've used quite a bit of sugar without trouble.

For your mash: I believe that's an appropriate schedule, although the protein rest probably isn't required.