I would return it and find something suitable for your dimensions. You don't want to chance it, fill up ninety gallons and discover all that water on your floor one morning. Even going over, like a stand for a 125g, you should be careful. Stands will be made to allow for particular stress on particular places. If your tank doesn't fit properly, then the stress of your tank's weight could hit a weaker spot. Do you have a shape weird 90g tank?
55gPLANTED:Rainbows/Loaches/Garras|30gVIV:Crestie|20gL:Leos|10g:Pearl Fighter|5g:Betta|5gChi:Spark Gourami/Badis|5g:ADF|2.5g:Betta|2.5g:Betta|