since a few people from the forum now also own the HP Reverb and may have a similar problem, I thought I'd post my solution here.
The HP Reverb doesn't fit perfectly for me. That's why I thought about the last days how I can increase the wearing comfort. My problem is that the headset presses on the bridge of my nose and so longer sessions are very uncomfortable. A few days ago I had the idea to try an old VR cover cushion (for the Rift CV1) in combination with the Rerverb. For the mod I simply used self-adhesive Velcro strips and attached the VR cover cushion to the faceplate of the HP Reverb. Due to the additional padding the headset sits a little bit further away from my face and there is no pressing spot anymore. In addition, the headset feels more comfortable for me without any changes to my FOV.
For me this is a good temporary solution until VR-Cover possibly offers an alternative faceplate. Now I can really enjoy the Reverb!