As suggested before, a horizontal bar can replace a lat machine (or anything else) when doing versions of a pushdowm. Not to mention, getting the center cable away from the face/head. If anyone would have trouble doing a muscle up to get into that pushdown position on a bar, than consider this. Set the pins in a power rack (or anything else handy) to about chest height, place a bar on them, and start from there. A 4X4, or such, can be used if desired. A BB tends to roll if not under complete control. Pushdowns can be similar to a dip with the knuckles facing forward.
Some BB'ers I've known have use a curl grip on the BB French Press behind the neck (touching the back of the neck each rep). Also when doing lat machine tricep pushdowns.
Thought the mechanics of using a DB with two hands seems reasonable, people tend to get very strong, very fast in that exercise. Having a training partner lug a 150lb+ DB high enough for a starting position can be one pain in the arse for both the spotter and the guy doing the exercise. From my limited experience, it's about 40/60 as to who uses a Olympic straight bar vs a Olympic style EZ bar. Don't see too many using a tricep bar, but that type bar would make more sense to me. Good luck.
