UKC

Situation summary.

About to be locked down. Live in an apartment block, great balcony. I want to install gymnastic rings suspended from the ceiling of the balcony. Needs to take a load of ~70kg. 
 

I can think of two options, try and drill and install bolts (but straight pull, length? Expansion, glue in?) or bond a piece of wood that I can the screw into... thoughts? 

Wooden bar with 2 uprights wedged between your balcony and upper one would be my preference.

That's how I put kayak racks into a previous garage without drilling into the ceiling.

Doubt your upstairs neighbour would want you drilling into his balcony.

Probably breach your lease too.