I hosted the Orphan Car Show in Atlanta for 16 years and we always pulled several KFWDHJ's but the bulk of the cars were Studebakers because that club is very active here. We also pulled a lot of Hudsons, Packards, Metropolitans, AMCs and, believe it or not, Triumphs and Opels because they have active local chapters. In the past three years, the Studebaker and Hudson clubs have had two or three combined meets a year with great success. The few Kaiser folks in the area (myself and Bill Tilden are members of KFOCI, SDC and HET and Frank Pudysz is an honorary member of the local HET) show up on a regular basis, sometimes bringing our KFOCI related cars.
I do not think an entire National Convention would be a good time for a combined meet, however if we go back to our traditional Thursday car show, we should invite them to show up and leave space for them to park at that time only. In Rochester, we had a Nash and a Graham show up and Pigeon Forge saw a Studebaker or two. At our local Dixie Kaiser meet a few years ago, we invited every local orphan club we could think of to show up at our car show in Woodstock GA. We were outnumbered, but we got to inspect Hudsons, Studebakers, a Nash and several others orphan makes. It's a great way to meet new people and see some other interesting cars.