Does remind me of a fellow who was asked to make one pile from two barrow loads of heavy wooden planks, one was nearly full and the other nearly empty, I kid you not he transfered the larger load onto the nearly empty barrow!!
We thought at the time he had one reasonable defence but nowadays it would not be PC to consider his nationality?!
Anyway, the reason this reminds me and despite all the obvious pitfalls of such folly, it does beg the question, why is the heater being used to heat the bottle? why not simply use the heater to heat the van????