Looks okay to me though I think i'd go a hemispherical RNFP... but then I am thinking smoothbore. Things are a bit different for rifled gun.
As for the HB and skirt, I'm with BB on it likely being best to heat treat. I haven't run into a skirt yet that hasn't deformed some if not heat treated no matter how thick it was, and still looked like an HB slug anyway. I fill the cavities partly to support the skirt but mostly to keep wads out of the cavity. Heat treated or not if the slug has a hollow base wads will try to get in there, even nitro card wads. You could copy the Lee Drive Key or get a tapered hollow bored/reamed into the core pin like the Russian Paradox slugs so the skirt could be thinner but the wad would be stopped by the central pin.
I wouldn't go any thinner on the skirt than 0.100" ... at least without a pin or "key", but that's just me.
If you don't fill or use the key/pin idea then put a tough disk like polyethylene under the slug. That should keep wads out.
As for weight, you could lighten some by using just two driving bands and leave a wide, and deep as Tom can cut, groove. The old Paradox slugs had a huge groove! They were solid body so heavy even if they were HP'd but a hollow base design would lighten them a lot. I've always liked the Paradox design:
https://www.classicshooting.com/coll...ant=1179491392
I'd stay away from too large a flat on top of the pin. I made mine fairly flat so keep lead in the nose but if I don't tip the mould a bit while pouring I often get a little cavity at the top due to air trapped over that big flat. Bubbles seem to flow off a radius or point but seem to hang onto the flat... at least in my mould. I think your radius looks good.
That slug would probably shoot just fine as is from rifled gun.
Longbow