This is a very well hidden path, IMO. It took me 2 days to see what to do. :O :))
I'm currently at 483, trying to get it lower.
EDIT (9 hours later): I then found another longer path and one more that I was able to optimize, first to 423 and then directly to 419 (never had 421). I don't dare say that's optimal, but I sure can't find more, atm.
Enjoyed it a lot! :)