Like most of you, I am experiencing indoor distance issues in e6 and HTH.
I have found that setting elevation to 6000 in e6 seems to make my distances more accurate for me for the whole range of clubs. For what it's worth, I have a garmin golf watch and have a really good handle on my distances on the course. Would love for HTH to add a elevation setting similar to e6 if the root issue can't be addressed because I am quite happy with e6 with this elevation setting.
Try it yourself and respond back with if it works for you.