Shortly I may be asked to build a semi/permanent theatrical stage inside a
church.
This particular construction has some unique problems/challenges.

1. The building is "heritage listed" which means whatever we do has to
'touch lightly' on the building structure.
2. The floor is polished hardwood.
3. The stage must not creak
4. It is essentially a platform 900 (3ft ) high, 5.8m (19ft) wide by 4.2m
(13 ft) long
5. It will be attached on the long side to an existing stage/alcove
6. Set construction crews being what they are, it may be necessary to
replace the (ply?) flooring on the top of the stage every five or six years.

I was thinking about laying down a ply floor on top of the original floor,
but not fastened to it, with felt underlay between.then ataching the posts
with triple grips to the ply. - I don't know if "triple grips" is a
universal term but this is something like what I mean
http://www.htp.com.sg/page2.html

Any suggestions?

Mekon