My experience is that one-designs can do fine in PHRF and the Sonar would seem like an excellent choice for Wednesday nights - very comfortable for a gang, small
jib, easy to handle.
That said, if you want to do well, get yourself on a Sonar that wins on the weekends and soak up everything about how they make the boat go. One-design racing has the benefits of pushing the performance of the boat and the tactics of the crew to their peak - if you can figure out how make the boat perform well and win in one-design, then you should be able to clean up in PHRF.