If you're not getting any flex in that aluminum, then it should be fine. MDF has its durability issues but as long as it's dry, it's ridiculously stable.
Thanks, it's only spanning about 36 in but there is about a 16th of deflection with my heavy duty router on board. I might shift the slab towards one of the weaker spots on my folding table because I figure the MDF will bend down there a bit and maybe I can match the slop in my rails with the slop in my table setup 🤣
100% that aluminum is flexing, the question is how much matters to OP? A CNC router has far beefier extruded aluminum gantries but still flexes from the weight of the router, although typically less than a mil. My guess would be at least 10-15mil with the aluminum angle.
OP said about 1/16", which would be what? 50 or 60 mil? Honestly, though, it's woodworking. In the right context, like coarse slab flattening, 1/16" might be fine, though I would reckon that the point where fine tuning by other means is not that bad would be closer to 1/32".
Currently yes I have it wedged underneath with a few scraps. It weighs about 75 lb and I'm going to be taking a thin cuts so I think it should be all right.