Hi Funkenhoser and welcome to HBT. Your first few posts need approval (we're fighting a battle against evil spammers) and I was happy to do so. I've also moved your post from HBT Announcements and Feedback to the Equipment subform, where hopefully more folks will be able to respond to you. I'm sorry that I'm not familiar with OBK brew pots. 15 gallons is a good size, I use 20 gallon brew pots and I never worry about a boil over.
I have one of the cheapish kettles from obk and I love it. 15 gallons, welded fittings that are super clean. I have had no rust issues and mine lives outside on the back porch all year, just a quick wipedown while I'm mashing and its good to go. They are also pretty easy to modify, I've punched like 6 holes between the 2 my buddy owns and its fairly simple with a step bit and a high torque drill
Edit: Forgot about the sale on right now. 80 bucks is a steal, I paid regular price for mine at around 120, still super worth it in my opinion
I've got 8g and 14g OBK kettles, welded and weldless. I personally prefer the punched out weldless. Easier to clean and easier to orient your thermometer and ball valve! Currently on sale - go get them! Cheers,