: Isn't an end pour a lot heavier than a little stick of cedar?

A light piece of cedar is only lighter than a heavy pour of epoxy. The density of micro-ballon filled epoxy can be made about the same as cedar. So if you fill the same volume the weight will be the same. Remember to take into account the weight of the epoxy required to glue your cedar stick in place and you end up the wood system might even end up weighing more.

A big heaving chunk of wood is heavy, and a small light pour of epoxy is light. It is not the technique that defines the weight, it is how much weight you add that determines the weight.

I mix up about 4 to 6 pumps of epoxy, add enough micro-balloons to at least double the volume (adding almost no weight) and when I pour, about 1/3 of the shmutz stays stuck in the pot. The result is void free, completely water-impermiable block just big enough to drill into that is perfectly fitted to the end. The only exposed wood when I drill the hole is the strips which are easy to see and seal. If you don't want as big a pour, mix less epoxy.

I can imagine good reasons to use a piece of wood for the end fill, but weight is not one of them. If there is any difference in weight it is measured in fractions of an ounce and is of no consequence.