I've had no issues with aspen, but am always open to new things. I'm actually getting another RHP in the coming days that I'll use in the vacant side of my divided enclosure. The plan is to experiment with all kinds of substrates and mixes to see what results I get.
25-50% in Summer. That's my Winter range. Yeah, take what I say on substrate with a grain of salt...
Oh, you might want to get a couple of these also: https://www.amazon.com/AcuRite-Humid...gateway&sr=8-1
I have two in each of my enclosures.