Priming with molasses

For my next brew I was planning on brewing a 5 gallon batch of vanilla stout. A friend of mine suggested I prime it with molasses rather than dextrose. Said it would give it a nice malty flavor, which is what I am aiming towards. Any thoughts/suggestions? And how much molasses should I boil before I add it to the beer?

One is enough. Hard part is getting it to stay in the water.

I would compare the ppg of dextrose to molasses and formulate a ratio.

I have three thoughts:

(1) It looks to me like molasses is only about 50% sugar, so I would use twice as much molasses as priming sugar.

(2) I don't think that the flavor contribution from molasses, used in quantities appropriate for priming, will be noticeable; I have certainly never found honey or belgian candi syrup to be noticeable when used for priming.

(3) I also think that getting the molasses to completely dissolve and uniformly mix in the beer will be difficult, leaving you with some bottle bombs and some flat bottles. Given my (perhaps totally wrong) prediction about the limited flavor contribution of priming molasses, I wouldn't take the risk of ruined bottles and personal injury.

Bear in mind that much of the flavor you like about molasses is due to the sweetness it has. Once that sweetness disappears - eaten by the yeast - what is left is a very bitter and assertive version of the molasses flavor. Hope you like it.