Bonding velcro to brass...

[KustomsbyKent]

I would recommend a VHB double sided foam tape from 3M. It is used commercially for bonding aluminum sheets together. I have used it in my corporate job as a design engineer, and spec'd it in for some aluminum assemblies, and it is a permanent bond! This tape also gets used on large enclosed trailers, and semi-truck van trailers to bond the smooth sheets to the structure, eliminating ugly rivets.
Cleanliness is super important with any adhesive, and particularly this VHB tape. Clean the surfaces with isopropyl alcohol, 90% is preferred, as the more common 70% has too much water. Once the IPA has evaporated, then you are ready to apply the tape. Use pressure after you apply it, as that activates the adhesive. Then, let it cure for 24 hours! This is super important, as it takes time to reach full strength.

Another option for you is to get the velcro with adhesive already on it. They make a heavy duty version that is rated for 15 lbs that I have personally used and it holds very well to aluminum. Again, make sure you clean the brass thoroughly before applying, and give it time to cure.
https://www.amazon.com/VELCRO-Brand-...0-eeda4dea34d6