Lovely bike! I have over the last few months tried a few front / rear tyre combos for a similar style of bike. Tyre combos are like bikes, except the equation is (n+2) to account for two tyres... The ones you tried are worth a go IMO. I have tried the HD (very good) ardent (OK at 2.25 for rear a bit slippery out front) rapid rob( for a race day rear only) and the high roller 2 both front and back (piles of all round grip but slow). I am currently on a slaughter rear and high roller 2...