pennywise is my favorite band!!!!!! nice to see someone else on here listening to them too! fletcher used mark IV's live for a long time, early 2000's he started using dual recs live, recently he has been using crate blue voodoo's mixed with rectifiers. If you are going for old school pennywise you've got the right amp for it. if you want new pennywise tones you need a rectifier.
Anyways, I owned a mark V for a bit. to get the pennywise guitar sound use the graphic EQ but dont scoop the mids out too much, fletcher likes his mids. he also strictly uses EMG pickups which affect the tone a lot. other than that i can't help you much with exact settings for your mark V. just remember to play super fast with lots of chugging palm mutes and that's pennywise! i bet there will be no one else on this board who listen to pennywise...too bad, they have been one of the most influential hardcore punk bands. been around since the late 80's. such a sick band