How much sugar to carbonate a Strong Dark Belgian

I know that strong Belgians should have a higher level of carbonation. With most of my beers, I usually use one ounce of corn sugar per one gallon (i.e. 5 oz/5 gallon batch). How much would you recommend for a strong Belgian Dark Ale? Maybe six ounces, or even seven?

Also, my O.G. was 1.090, which will give me somewhere in the vicinity of 9% alcohol. I'm planning on leaving it in primary for about four weeks, and then straight to bottles, with no secondary. Do I need to repitch more yeast for carbonation, or should I be okay with what's in there?

DIY:
http://hbd.org/cgi-bin/recipator/recipator/carbonation.html

and definitely use strong bottles.

For all my beers that I bottle condition, I go for 2/3 cup dextrose or 1 and 1/4 cup DME. I have made many strong belgian ales and use this priming amount and the head is excellent, as well as the carbonation level.

http://www.tastybrew.com/calculators/priming.html for the amount and http://www.bjcp.org/stylecenter.html for the proper carbonation levels for style