Hi nk3t
Thank you for an excellent report. If Hayes allows the referenced seam to be exposed on the surface the O-ring bears against, they are idiots. A cutting reamer or a hot tool would eliminate the seam at little cost; an O-ring seal needs a good surface to seal against. I just looked at one of my used Hayes tanks, but I did not want to take it apart to look at the surface in question. Next time I'm at the hobby store I will look at one. I may even send Hayes an inquiry e-mail. Have you ever seen the Sullivan large white plug shred as I described in my earlier e-mail? I don't really remember if it was a Sullivan; it was the large plug and was white. I do not purchase cheap, unknown things for my planes.