Thanks. Interesting no mention of wimberley or 4th Gen or ...
Wimberley doesn't do a replacement foot for the 500/4, they recommend the P-40 plate, and you asked about a replacement foot not a plate.
The 4th Gen foot is more like a plate than a foot, but one that bolts directly onto the mount. I think they do that for the superteles so the big diameter lenses are centered over the Mongoose head (Wimberley has that issue with their Sidekick and Side Mount heads, and they recommend those flat 'feet' for the 400/600/800 lenses, but not the 500). I don't like that design, because it means you can't use the lens foot as a handle to carry the lens.
Like I said...RRS or Kirk.
Hi RGF, I've changed all my Big White feet with the RRS Foot replacement, I tried the Wimberley Plates but just wasn't satisfied with the set up, the RRS replacement feet have worked exceptionally well, very Happy. The attached is the RRS foot your looking for, I don't have experience with anything else to compare.
For loosening stuck screws I've found this works for me, Place your screwdriver head into the screw, then a sharp tap with a Hammer (sharp tap, not an all out Arnold shot), if this doesn't loosen it, try soaking the screw area in WD40 overnight.