Jeff-
Just got a whole load of stuff from Aus including a bunch of these! Send me your address and I'll send you one. I've been using the "pushup" on my sloop mast for years and halyard on my cat mast last year (I have a cat rig main with a rope luff for this sail so can't be "pushed" up) and I LOVE the "pushup"- No halyard to tie on/off or worry about losing/fraying/tangling/etc. I've even raised/lowered on the water (not easy though but can be done).
There are some "tricks"- The foam should be situated under the shackle of the ring/loop so there is more projecting to the rear- only enough in front of the shackle to keep it there. It should be very snug and centered over the masthead plate and hold the ring straight up. I always sort of "force" the ring forward as far as it will go before raising the sail (look at the hook at the top of the sail- it does not project out far and the ring must lie close enough to the mast it "catches" on the hook). Sometimes the ring will not seem to want to catch on the hook, it appears to be held off to the side - I just make sure the sail is all the way up and then "flick" the mast slightly side to side and it will usually catch then. You also need to make sure your luff tubing is not broken and is relatively "straight" (it will tend to take a "roll"- carefully sort of flex other way before raising). I still have my ORIGINAL Kevlar/mylar Goodall sloop main from 1997 that has been repaired and it catches just fine- sometimes even with the dang mud-dobber wasps making a home at the top of the mast groove! I have added non-slip on either side of the mast on my front beam and always stand straddling the mast, grab under a batten with fingers on each side and slide up, if you have quite a bit of prebend it will get tough at the end- so get that last batten a good hold and slide it all the way up. Another Aussie trick is to use your tiller (another reason they like them long and easily removed!) under the highest battencap you can reach to get it all the way up. Make sure the boom is not attached to the sail when raising or lowering, the boat is DIRECTLY into the wind and the mast is free to rotate.
Coming down is easy- take downhaul off, remove boom, straddle mast, push up as far as can, hold there, rotate mast ~90 degrees quickly (it sort of "pops" the ring out) and pull down. Other way is to use tiller to push up from tramp then rotate quickly and drop. Remember too to remove the luff from below the slot first so it can come down and out of the mast- I usually sort of "flake" the main as it comes down, using one hand to provide some tension so it doesn't just fall down.
The foam you want is very "closed cell" (ie dense)- I have used stiff syrofoam in a pinch but "flip-flop" or old black wetsuit material would work fine. Upholstery or "sealing" foam is generally too spongy and not stiff enough.
Hope this helps-

Kirt