I have done the same as Winpro last year. All my gear from Tool-station, mechanical flange, heat resistant cable, waterproof sealer and hole-cutter for drill. I researched topic fully from threads on the forum

, cheers. The biggest leap of faith is cutting the hole in your precious tank

, no joke, when I was doing it my heart was thumping, but it worked out nicely. By plugging it in for a few hours before bed time kept ice off and few hours before going out in morning, water warm enough to keep pipes supple and keep pipes from icing-up, works great. Mechanical flange is better option than straight fix of element to tank because if element fails you can easily screw it out of flange and replace it