Let's say each pallet weighs 3 tons. Six pallets high is 18 tons = 36 kips. Put that on square yard of concrete it comes out to about 30 pounds per sq.in. Structurally this is nothing. Everyone likes to go goofy over gold. Gold salesmen know this.
Per the link ...
Total Gold in Trust:
Tonnes: 232.32
Ounces: 7,469,219
Value US$
3,851,491,895.52
IIRC, one tonne = 1000 kilograms.
There's a prospectus available at the link which I cant download due to time problems (other things to do) but taking a non-engineer approach, it's most relevant to note that this is a NYSE company which is filing SEC reports.
That means an outside audit firm is certifying their financials. Auditing 101 requires the auditors to verify the inventory. If the auditors are sane they would count every single bar, weigh several picked at random and send several random bars to a professional gold assessor before signing off on the financials.
Both NYSE and the SEC are not entities to fool with and blatant inventory fraud is too easy to detect.