There are a handful of lakes on the ranch that are pay to play, but the two that are best known for especially large fish are Minnie and Stoney. I don't know how much snow they've had up there this year, but those lakes are at ~3500 feet, so depending on what part of May you're looking at you might be there after ice out, and if so hopefully after turn-over. Scuds, leaches, dragon fly nymphs, blood worms and chronis are all usually on the menu at that time of the year. If it were me, I'd plan on blood worms (red D-rib over red holo tinsel) and chronis (I've had luck in the clear tannin stained waters in that area with a dark olive body and chartreuse rib), with balanced leeches and boobies as plan B. That said, I'd keep an eye on the reports on the BC board and do a little research because you may need to have some lower elevation destinations in mind as a back-up.