We have 2 members here (besides myself and my cousin Ed) who are very likely U106 positive. Those members are kit numbers 18688 and 168469 and belong to paternal ancestors listed as Thomas Holley and John Thompson respectively. The indicator is that your STR DYS492 = 13 and although I don't remember the exact percentage off the top of my head, over 80% of people who have this value are positive for U106.
I highly recommend that you join the R U106 project at FTDNA. I am also a member there and it is a very helpful and excellent project. It is very active with well over 3000 members and growing every day. The administrators are second to none and I believe they likely out class any others. There is also a Yahoo groups link for them listed and a lot of valuable information is discussed. The admins there give excellent advice on testing for the best value will be happy to give you free personal advice to help you make the results you get be useful to you. Here is an excerpt from their overview page.BEFORE ordering the wrong SNP Pack, only if you are positive for U106 (also known as S21) OR are in R1b (R-M343), usually predicted for R-M269, and have the result at the 66th STR marker where 492=13, OR have the result at the 2nd STR marker where 390=23 AND the result at the 18th marker where 447=24. However, we have a mutually exclusive arrangement with the U198 and L1 Projects, so we cannot accept those who are positive for either of those SNPs. Big Y or SNP Pack testers who are U106+ (U106=T) are definitely requested to please join our project.
Here is the link: https://www.familytreedna.com/groups/u106/about
I would also like to ask both of you if your paternal ancestor listed is correct for the STR results posted on our results page or are they actually from an unlisted Harp ancestor. If they are from a Harp ancestor, please let me know the name and I will find a way to get the correct name associated with the results.