1/4 keg Heating Element?

[Redeye]

I am looking to convert my 1/4 keg boiler to electric. Most of the elements talked about fit the full size kegs. I was just going to buy one of those and a bend it up slightly and just leaving enough room to be able to tighten it without it hitting the bottom. I know that is overkill for a small keg but i didnt want underkill if you know what i mean. Any suggestions will be greatly appreciated. Maybe if i understood what wattage would be enough to boil about 5 gallons of water i would be fine. I am going to be using the HF controller. I found this on ebay http://www.ebay.com/itm/Camco-02203-200 ... 53f5431937 This is 2000 watts with a minimal of 9 inch tank diameter. Thats a 2500 watts under the normal ones that are talked about on HD. Thank you for your help