I've been a little busy.
Firstly, at Sharvil06@NH's request, I made some stemless molds. They make sense, really - I break off the stems when I'm done anyhow, because I can't melt a straight and centered enough hole in the foam.
My take is that I like the automatic limit that the stem hole provides. I fill the mold until it overflows a bit, then I know I'm done. With the top open, I need to be more careful not to overfill. However, there is one advantage - I don't have to cut the mold. It's cup-shaped, and flexible, so there's no trouble removing the molded hot glue head.
Second, I had some leftover putty from making these molds, so I made heads out of them. Fortunately, silicone putty doesn't form bonds with cured silicone putty. It does stick, but didn't ruin the existing molds.
I found that it did bind very tightly to sticker backing paper, such as the brown slick paper that McMaster felt discs are sold.
They formed very nicely, and seem to have a decent mass. If anything, they feel heavier than hot glue domes. They have a lot more give, being rubber. In fact, they bounce. There's only one problem: being silicone rubber, NOTHING STICKS TO THEM.
No pics because they look like normal nutheads, just purple.
Third, I did mention I had leftover putty, right? Does this shape look familiar?
Yes, it even has the stupid little air hole. (I'll take a pair of nips to it later.)
On the subject of streamlines, someone asked me if these heads would work in stock blasters. Well, the heads are a bit longer than stock streamline heads, but if you trim 1/4" off the foam, it works great.
However, I don't have any decent CS-x blasters, so I can't say how well they fire. They seem to perform about as well as stock foam, so I'm guessing a modded LongShot will be able to make them really scream.