@Beff Juckley,
If this is going to be your very first venture to the 5 string world, don't worry so much about the string spacing. You're required to adapt anyway. You'll need to get used to the additional low-B string and the fact that the low-E isn't the closest string you see anymore. And more importantly, you'll need to relearn string muting techniques.
Unless you are a crazy slapper, tight spacing like 16.5mm will actually brings more benefits: the neck wouldn't be so wide, you can still practice string muting for the low-B with your fretting hand thumb, the closer strings will alow faster playing, narrow-neck allows somewhat lighter and less prone to neck dive instrument, and with times, you can even play slap lines on a tight spacing with no problem.
I didn't notice the string spacing on my 1st 5er bought in 1992, which had 18mm spacing, or my 2nd 5er, an ABG bought in 2014, which has 16mm spacing, until I got some 6ers which had 16mm string spacing. Mainly, because it became harder to play slap lines cleanly. At first, I blamed the tight string spacing. But then as I got more 5ers, 6ers and 7ers, which string spacing varies among 10.8, 16, 16.5, 17, 18, and 19mm, I began to realize that it's the muting techniques that I need to really pay attention to in order to play cleanly on multi string instruments. No matter I play them finger style or slap and pop (I don't have any desire to play bass with a pick, despite owning so many, as I was a guitar player in my high school class band).