My four 5-string Wals all have 16.5mm spacing.
Mark II 5-strings do tend to be heavy...I have two of them...and some are well balanced and some have heavy headstocks, thus neck-dive. I have mitigated this wonderfully by replacing the tuners with M4S Lights from Schaller. These are direct replacements and look exactly the same as the original tuners, but are much lighter.
My Mark II 5s sound and play great. So much sound, booty, growl, punch, clarity,...you can get so much from them. I haven't played any other bass that can match a Wal for its true "bass-ness."