I dont know guys, I have a standard Keg, and have had that thing up to 14.5 gallons with a 90 minute boil for a 10 gallon batch. I think you will be limited if you use it.
Just my opinion, but I would get a larger Keg, convert this one as well and use it as a HLT, or a MLT, it will work great for that.
Again, just my opinion.
No matter how much money you THINK you are saving by brewing beer, you are still just pissing money away