Rabbit, I'm actually demoing the IG Prestiges and the Bio. 300 this week and really like the feel of the Head leather myself. I have TW leathers on my Londons, but they push the balance a little more headlight than I want to go. Maybe I got the medium thickness; I can't remember.
Do you happen to know the trimmed weight of the Head leathers? If I stick with the Londons, I may go this route, as they're reported to be lighter, and the feel is exceptional; that I do know.
I'm actually leaning towards buying and modifying a Bio. 300. In that case, I'd most likely go with Volkl leather for more weight and headlightness, as I put quite a bit of lead in the head of Dunlop 300's. As usual, thanks!