I asked Pete for those dumps years ago and he said he'd lost them.
And that's why you upload dumps to the Internet
Guess, he has lied 'a little', since I've found the site that sells a multicart with all these titles since 2014 (out of stock atm, though) - http://www.multimax.co/
The 'Download' section has a EPROM image for that multicart, I've downloaded and split it, it doesn't have any compressed data, only a series of ROMs going one after another - https://www.sendspace.com/file/saf8rk
Notice, that Bowling has its 'lorom' ($8000-9FFF) part omitted (http://c64preservation.com/dp.php?pg=ultimax
has it described as 8k, not 16k); Radar Rat Race (Alt) is omitted (1-byte difference to Radar Rat Race 2A, bad dump?) and Radar Rat Race (Jpn, v.02) is omitted (1-byte difference to Radar Rat Race 2B/Radar Rat Race (Jpn, v.02, Alt), bad dump?).
Also I'm not sure about the chip/ROM sizes, http://www.multimax.co/hardware/
describes Ultimax carts as a pair of 8KB banks. Is it correct to have Music Machine and Pinball 'lorom' as 4KB and Slalom 'lorom' as 4,5KB or should they be padded to 8K? c64preservation.com only describes the program sizes, not the ROM sizes.
Wiki - https://ja.wikipedia.org/wiki/マックスマシーン and Game Nostalgia - https://web.archive.org/web/20160319135003/http://www.game-nostalgia.net:80/max/max.html sites also have the 'Poker' (ポーカー) game listed as released, so, maybe, it should be added into the 'Games needed to be dumped' list? There's no scans/photos of it, though, so it's unclear, whether it exists or not (though, Gorf, Billiards and Slalom were 'unclear' 'rumored' titles with no photos as well until found and dumped, so, Poker has a good chance to exist as well).