A Modulus Quantum 6 was my "gateway" to 6 string bass which has 17mm string spacing and 35" scale. They're worth the experience to see if you can handle a 6 string bass with the tighter string spacing which helps out pretty huge. The 35" scale was an absolute non-issue for me. Other players may find a reason to make it problematic simply because it isn't 34" scale and feeling like "home". 3/4 Upright has been 42" scale forever...and it's a great hand work out. Your hand will adjust with a bit of work or you'll find out immediately it doesn't!
I couldn't play 19mm 6 strings at all. I've owned two 19mm spaced 34.5" scale F-Bass BN6's in my time that I sold because they didn't work out for me. The neck width is just too wide and uncomfortable for me to play but it took me twice to figure that out! I've had the pleasure of playing a friend of mine's Fodera Anthony Jackson Presentation 6 which is 36" Scale and 19mm spaced....now that bass is a real "handful" to play. Plus being different as they're chambered and passive (not to mention quite expensive!)
I just had a Fodera Tony Grey Signature which is a Monarch Elite 6 stringer with 17.5mm spacing and 33" scale which was a blast to play, but obviously lots of $$$. I had to make a choice between the Monarch and the Wal, and the Wal won! The Wal 6 fits like a glove although I highly recommend trying out a Q6 first. It's the only way to be sure before making a big investment.