Add it.
Suggest just crunching for HCMD2 and keeping a very low cache (0.01 days).

I agree. A small contribution beats no contribution!

Two of my crunching machines are dual-core Atom mini-desktops, one a D510 at 1.6 GHz and the other a D525 at 1.8 GHz. They were bought for purposes other than crunching, but there's no reason they should be idle when not in use for those other purposes so they crunch most of the time. They're not fast, but they're reliable, and they run cool enough that I can keep them crunching in summer. I run mostly HCC, HCMD2, and C4CW on them.

After posting this message, just for the heck of it, I looked up the device statistics on my Atoms:

kate-zotac64 6/6/11 3:100:01:56:15 704,970 2,072
kate-jetway64 6/6/11 2:159:23:55:56 625,262 1,605

So between the two machines there are over 3600 valid results returned and 1,300,000 points earned. To me that's worth it.

Edited to add device stats.