Should I use the direct mail appeal predictions for In Memory mailings?

You can, but this depends upon your objectives. You can build your audience using:

• Mail Appeal ranks to identify the donors most likely to respond via mail
• Filter using the ‘In audience’ filter if you have previously created an audience of In Memory donors, the ‘Inclusion in past campaign’ filter if you want to filter only to donors who gave in certain campaign, or the ‘Constituent Code’ filter if you have a specific constituent code for in memory donors (note: constituent code filter only available for certain CRMs).