Various options if you look through this thread, but I think I’d use what FE posted, (studs welded to circular plates, which are available with plates up to 2” diameter I think) and bond them on with one of the rubbery adhesives that come in mastic gun tubes. Some of those are super strong.
these are they..
Stud permits clamped attachment of systems to structure or securing of enclosures or other modular equipment. Supplied with disposable installation fixture.
www.clickbond.com
And I have used this with great results..
The Fix ALL range of hybrid polymer sealants and adhesives from Soudal are the perfect answer to all interior and exterior bonding, filling and sealing jobs. Use on porous, non-porous, wet and humid surfaces, even underwater.
www.soudal.co.uk
see a Demo..
Cheers,
cliffa.