I’ve got an end fed half wave for 40m strung up in the loft area of my garage, but the way my attached garage works, it’s dry walled up there. I’m having trouble being heard and I’m wondering if this is part of the problem.
Another thing that is working against me is my power supply isn’t delivering max power to my G90, so I need to fix that too!
Gypsum board isn’t going to help but I would look into your power supply first. If you’re not getting ~13.8V (per rig’s specs) you aren’t going to get good performance. Also, consider your roofing material, height from ground, and proximity to metal/wiring because they all can muck things up.
There is a chance, based on antenna’s height, you have a quasi-nvis antenna that isn’t getting enough power and the signal just isn’t being heard because your propagation is close to home (regional).
Having said that, I used a 10m dipole with my G90 for about a year (I used the tuner to get on other bands) and it was in the eave crawlspace of my Cape (up ~10ft-ish). I did reasonably well all things considered but it was somewhat directional.