well first off get yourself a set of dyno jet needles...
they have a lil different taper to them then the stocks and also have 6 positions for adjustments.
second.....you see my mods in my sig,so u can use this just go a lil leaner then me for your elevation since im at 850-900 ft above sea level
i run stock pilot..310 mains in winter and 300 mains in summer
and i also run dyno jet needles in the 3rd clip position from the top
i would start with the 260's u have then do plug checks from there.....your plugs will tell you everything you need to know
Dan