So, I ordered an Orphan Espresso 3rd Shot to help with temperature management on the 51 mm Millennium group of my Gaggia Factory. The heat sink is designed for a 49 mm group, but with some filing of the ears, it can fit the Millennium group. Here's the sales pitch from the OE site:
The OE 3rd Shot is a solid aluminum heat sink designed specifically for use in Olympia Cremina, Elektra MCAL, La Pavoni EPC8 and 16, and other machines using a 49mm filter basket (small group home lever machines) to approach the problem of group overheating when multiple shots are pulled.
It took me a couple of days of filing with the file off my Leatherman Wave as well as a Dremel cut-off wheel to get the ears to lock into the group. The filing wasn't the prettiest (my issue) but the heat sink is fitting in the group now. So far, though, I haven't had time to really play with this to see how effective it is for cooling the group. I've been giving my bottomless portafilter a cold water bath between shots and locking it into the group while prepping the basket between shots which seems to work pretty well, but there were some days that it was a struggle to get the temps down. I found a home for the heat sink in the freezer and I hope to have an espresso session this weekend to really try it out. The new low-temp 60 - 90 degree LCD temp strip should also help really dial this in.
I'll use this thread to post updates on my experience. I had ordered a full, spouted portafitler for the Wife to give to me for Christmas for this purpose right before OE came out with the 3rd Shot, but with my Niece moving in and all the boxes around the house I haven't even been able to find it. The photos below link to the OE site.