How's this for a Belgian Strong?

[bjornkri]

BeerSmith 2 Recipe Printout - http://www.beersmith.com
Recipe: Urbs Vetus Obscura
Style: Belgian Dark Strong Ale
TYPE: All Grain

Recipe Specifications
--------------------------
Boil Size: 25.79 l
Post Boil Volume: 23.75 l
Batch Size (fermenter): 20.00 l   
Bottling Volume: 18.49 l
Estimated OG: 1.085 SG
Estimated Color: 68.3 EBC
Estimated IBU: 27.5 IBUs
Brewhouse Efficiency: 68.00 %
Est Mash Efficiency: 79.0 %
Boil Time: 60 Minutes

Ingredients:
------------
Amt                   Name                                     Type          #        %/IBU         
5.00 kg               Pilsner (2 Row) Bel (3.9 EBC)            Grain         1        62.5 %        
2.00 kg               Vienna Malt (6.9 EBC)                    Grain         2        25.0 %        
0.24 kg               Caramel/Crystal Malt -120L (236.4 EBC)   Grain         3        3.0 %         
0.08 kg               Chocolate Malt (886.5 EBC)               Grain         4        1.0 %         
0.68 kg               Candi Sugar, Dark (541.8 EBC)            Sugar         5        8.5 %         
20.00 g               Magnum [14.00 %] - Boil 60.0 min         Hop           6        24.7 IBUs     
10.00 g               Styrian Goldings [5.40 %] - Boil 20.0 mi Hop           7        2.9 IBUs      
1.0 pkg               Trappist High Gravity (Wyeast Labs #3787 Yeast         8        -             


Mash Schedule: Single Infusion, Medium Body
Total Grain Weight: 8.00 kg
----------------------------
Name              Description                             Step Temperat Step Time     
Mash In           Add 19.09 l of water at 73.1 C          66.7 C        60 min        
Mash Out          Add 10.69 l of water at 93.7 C          75.6 C        10 min        

Sparge: Fly sparge with 4.29 l water at 75.6 C

I've been going back and forth with a few things, such as whether to add wheat or not, how bitter I should make it (feel it's at the upper and right now) and how much chocolate malt to use. I'd like it to have a bit of a "bite", but not to get roasted or ashy.

Any final tips? 5kg Pilsner malt is a hard limit because that's all I've got, everything else can be bumped up quite a bit as needed. I would have liked to use Special B but am all out so I'm hoping Crystal 120 will kind of work as a substitute.