I was intending to try to get the o-rings that go on the OEM block plugs, and put them on the Fumoto valves. Didn't end up getting them. Local dealer didn't have them in stock and I couldn't figure out how to order them online from Tousley. Bought a "Under Hood Assortment" of o-rings from AutoZone and it had two that fit. I had thought the kit had two of each size, but that's not the case. So I have two different sizes on there and they both work.
The one under the starter was in a very inconvenient position when turned down to stop. I backed it out half a turn and it still seals, and now I can reach it easily.