The small leak at the uniseal will not affect the performance of the skimmer if used in sump. It would only be a problem if it was to be run stand alone outside the sump. Things would get wet. You will get some salt creep buildup at that uniseal though.
I have an older Euroreef that I modded to be a recirc skimmer. It has several leaks like you describe.. the thing skims like you can believe, but it has to be run insump because of the mess it would make outside a sump.
Dave