I did mention earlier that I felt that there was a bit of flex in the front of the Tikit. I suspected that it came from the aluminium riser tube that was used. When converting to single speed, I took the opportunity to play with this.
My parts box had a nice long quill stem from an old mountain bike with 1 1/8" steerer. So out goes the aluminium riser and ahead style stem. Slip the quill stem straight in the top of the hinged steerer. Since the steerer is designed with a slot so that it can be clamped tight onto the aluminium riser, you can't use the internal expander bolt, so I discarded that and just used the external clamp to hold the stem firm.
... and yes, it's a lot stiffer.
Depending on your riding style and the length of the hinged steerer, this might not work for you. I'll grab a photo of the whole bike as soon as I can so you can see the sort of handlebar height that I end up with.