[RTTY] Getting spotted by RTTY skimmers

[Rudy Bakalov via RTTY]

This may seem like a silly question, but I will ask it anyway: how does one get spotted by the RTTY skimmers? Is there a "trick" to it?
I am asking because upon reviewing skimmer data for CQ WW RTTY on 80m I realized I was spotted only twice. No, I don't have a farm of antennas, but have a decently performing inv-V with an apex at 90'. Running 1500W.
Just for kicks, I switched to CW and the call sign I used got spotted by a dozen or so CW skimmers with SNR between 20 and 40 db. So my signal is loud enough.  Then I started digging even further and noticed that the stations that were calling me got spotted, but I did not.
I tried different permutations during the contest: CQ call call CQ, TEST call call CQ, etc. None of them made any difference.
Any thoughts?

Rudy N2WQ