Matt, put your glasses on and look at the picture again!
Yes, there are cross pieces on the bottom of that ramp.
Just inside of where the end lip/hook is there is a re-enforcing cross piece.
About two inches in.
If there is one, there is probably more.

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WA. state, 1 mile south of the Canadian border,
I am not at the end of the world, but you can see it from here.
'66 Monza Coupe - 4spd, 140 Daily driver beater
'67 Monza Vert. - PG, 140 Daily driver beater
'67 A/C Moredoor Monza - 140 4-spd. driver

Drill a bunch of holes in it and install bolts with the shank up so that they protrude about a half inch .

It doesn't look like that any material can be added to the ramps to help out in driving up the ramps. The added material will prevent the ramp from sliding into the storage slots.

Blast the paint off the ramps and apply walkway anti-slip paint to the ramps. It will get you going for now, until thinner ramps with expanded metal can be made.

Al Lane
Ellabell GA

1966 Monza Coupe, 110 hp, 4 Spd
1968 Camaro SS Coupe 350 CI 295+ HP PG
1964 Greenbrier Deluxe, 6 dr, 80 hp car engine, PG
2015 Chevrolet Malibu 2LT
2018 Chevrolet Silverado LTZ Z71 Centennial Edition
1947 Farmall A tractor 15 hp

Probably the easiest way to fix this is to just weld some expanded metal on top of the diamond plate if the ramp storage tray can handle the added 1/4”.

You never mentioned snow on the trailer. If you move to a Florida, you won’t have that issue 😎

64 Greenbrier
64 Spyder (needs restoration)
65 Corsa 140, restored
66 Corsa turbo, restoring now
66 Corsa 140 "RR" code coupe fully restored
67 Pontiac GTO restored
69 Corvette 427 convertible restored
2015 Porsche Panamera S
2015 Corvette Z06
1965 AC Cobra (Factory Five)

I loaded the trailer in Raleigh North Carolina, and it was pouring rain, luckily I vidded it so you can witness what I went through, but not the part where it slipped off. And there's probably room for the extra 3/8" expanded metal in the slots. But I'm thinking the anti-slip paint is a simpler solution. I'll look into it, I have a trailer with a loading ramp with expanded metal, and even though it looks rough, it's very slippery

On ther expanded metal ramps you have. Coat them all over with automotive underbody rubber coating. You want the rubbery compound. Anti-slip paint would come off to easy. Rubber compound would be better and be less slippery I think. Might be wrong, so try a small section first.

Al Lane
Ellabell GA

1966 Monza Coupe, 110 hp, 4 Spd
1968 Camaro SS Coupe 350 CI 295+ HP PG
1964 Greenbrier Deluxe, 6 dr, 80 hp car engine, PG
2015 Chevrolet Malibu 2LT
2018 Chevrolet Silverado LTZ Z71 Centennial Edition
1947 Farmall A tractor 15 hp

Good idea, a bigger problem is the tailgate-ramp should be a foot longer, it's too steep to walk up or pull a hand dolly up, I just thought when I had it built that 5 feet would have been too long, I was wrong

Don't drive onto the trailer. Install an electric winch and pull it onto the trailer. Problem solved.

I'll get some better pix during the daylight hours, and I'll make a video as well. The ramps are strong enough, they just are skikky skikky skiddy