You should be okay.
I live on the 4th floor. Wood frame.
180 with 33 sump and 45 top off in the "dining" area.
135 FW and 90 FW Discus tanks in the living area.
135 FOWLR in the bedroom.
Oh ya, and a 10g goldfish/feeder tank, if that counts.
Haven't heard any creaking yet.
Just make sure your system is resistant to overflowing/flooding as best can be and you shouldn't have anything else (read weight) to worry about, IMO.
Cheers
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