I do not use my A/A stems in my Plenty any more (except for one broken stem), not after breaking 2 of them in it, one actually shattered while using it, the other just broke pushing it in too hard, trying to get a seal.
One good thing came out of that though, only the bowl broke off my bent stem leaving the 4 holes flush. I attached the Plenty mouthpiece to the 4 hole bowl end with a bit of silicon tube and put a silicon tube on the usual mouthpiece end of the A/A stem and that goes into the black filling chamber cap. A nice glass bent mouthpiece that does not leak or explode while using, I also like watching the vapor travel through it and can tell when it needs cleaning, which is easy.
Oh, I did get the dosing cap to fit, I will add that to the tally on the weekend, it might take a while to get through(Thank goodness for rubber bands and an easily defeated dead man switch).