I’ve had a Surco (a 50”x60”) mounted on Yakima load bars for several years and used it a lot, until a couple of years ago. I was always quite pleased with it.
Roger is correct... it’s not as sturdy as, say, the Confer on my FJ40.
I bought extra floor slats... less gaps and more stability and mounted the basket to the Yakima loadbars, with U-bolts and that stiffened it up even more.
Ive used it on my Tundra’s SnugTop topper, which has built-in locking Yakima mounts... and is rated for a max load of 250 lbs... I think the Surco has the same load rating.
Sorry... I have no experience with the Surco mounts.
I haven’t been able to lift the rack, to mount it to the SnugTop for a couple of years due to back problems... so, I would consider selling the Surco... but, WITHOUT the Yakima bars.
PM me if you need more info.