Exactly! Which is why anyone who complains about getting shot with a frozen paintball is an idiot, because they shouldn't be playing paintball at all! Whoever designed a paintball to break when it hits a target should be shot.. With a frozen paintball!
What kind of wusses are nerfing today that need it softer. The only problem I've ever had was not feeling it through my clothes. If these people are too whimpy to take a unsoftened dart they shoudn't even bother nerfing at all.
...Anyways, I found I could get the foam fairly straight by using a hair dryer (As recommended by... I forget who, but I always traced it back to you, Stefan). Made a little box setup that uses the air flow from a hair dryer to cycle the foam and prevent melting, too. Though some of the little foam stubs retain a certain bit of bending, this can easily be corrected with a while it's still hot. I've found this technique to work a lot better than mechanical straightening, and be completely permanent. I'm using RCR brand foam backer rod (this technique works both on the old, light grey kind they had a few years back, as well as the new darker stuff).
I think I mentioned this, but I always just put a ~.5cm long disk of Foam Backer Rod (Hereafter referred to as "FBR"), that is one size smaller in diameter than the dart itself, on the tip with a little more hotglue. This tip comes off from time to time pending spread (and "m4d gr4nny hot gluing skillz"), but it's really cheap. For example, a 5/8" FBR dart would have a ~.5cm tip of 1/2" FBR.
PTEG as a material does kind of suck. If we just want a body, and don't really care about the barrel type or diameter of the dart, we could just work with... Oddly enough... A McDonald's or equivalent diameter straw, using 1/2" foam with an embedded weight as a tip. The obvious problem with this, aside from the larger tip's interference with clip setups, would be the small diameter. Which raises the actual point of this rambling; A new requirement for this new dart modification:
How large in diameter do we want these darts, bringing into account safety concerns?
A dart using 1/2" FBR can potentially take out an eye due to the localization of the same force of a larger dart [with the same mass] into a smaller area.
I know from experience, as a reference, that a Super Maxx 1500 with a single barrel, using a 1/2" FBR (~1/2" diameter tip), .5cm foam tipped Zero dart, managed to do substantial damage (and a week after medical observation, happily temporary) to a participant's eye through his eyelid from a range of about 30'. This rather tragic event implies that we need darts that are either larger or lighter.
Lighter is no problem; Hollow out the foam with a drill bit or straw to allow for a lighter tip weight. The decreased dart mass, however, decreases the range noticeably. In my unofficial trials with a Secret Shot 2 there was a range difference of about 17% going from a size 7 lead fishing weight to a single steel bb (A measured range of about 110' or so to about 90' or so unmeasured [compared against the heavier darts... Unofficial, as I said]).
Wider could lead to some fun. Imagine a 19mm round in a rather large homemade air rifle that can get ranges around 200'. Insane, right? But at the same time, with the large amount of padding and weight such a wide dart allows, safe. Of course, this brings aerodynamics into the equation, but that will be dealt with as that tangent is explored. The materials are certainly there.
Looking at the masses of darts and available materials, I'm still a big fan of just using shells, rather than building the shell into the dart.