Oh right, basically air with a bit of plastic mixed in (I completely looked over the HDU mention 
)
Well it sounds like you’re getting a good bit of experience under your belt. When you feel you’ve got it really dialed in maybe you could update your post from a couple weeks ago 
I’ll have to get some HDU to play with for 3D carving, looks like a blast with very little chance of catastrophic failure. Oh maybe it’ll be good for painted topo maps since we can move through it so quickly! 