I've built an early 18" 1993 rts-1 (team) with a indy @ 63mm -works well.
I've owned a 20" 1995 rts-3 with a xc 700 later a judy DH - worked good with the marzocchi, ok with the DH.
z4 sounds ok and best in my ears. - early fork, tiny travel. judy race (what year ?) would be too much i.e...