I like the 19's on my 18, and those Michelins do have some good grip on the track. I'm not a fan of the staggered sizes though, I like the option of being able to rotate my tires to get that extra life out of em.
Seems most track guys don't want anything bigger than 18 and will tell you 19 and 20 are for car shows and cruising. I know Kenny Brown thinks track cars should have nothing bigger than 18" on them. I say drive with what you are comfortable with. I drive with hand controls, I'm not out to be the fastest guy on track or set any records, and have no issue with 20's so I've just never felt the need or the expense to change.