That hole cutter looks like a 12" - which will work - but you will want the hole cut low down and as it spins round it will hit the van floor. Try to get a 6" one.
I couldn't - so bought the 12" and just used a hacksaw to cut it down to a smaller one. Simples.
I emptied the tank - it was quite a job - and removed it to cut the hole; unfortunately I cut the hole too big; I'm a Geordie.
I measured the hole I wanted using the O Ring thingy; the flange; using the tips of cutting tool. Unfortunately I did not notice that the cutting tool widens at a point lower than the tips, which meant my hole was bigger than the tips!
I think it'll be okay; I covered the seal with an exterior silicone filler, last night, but it's still tacky and I want to give it 24 hours before I re-fill my tank.
It'll be Spring before I get out to work at this rate!
