Eric7, what name brand riser did you end up using? I have a 6.5" Delta on my Rover ST and I like that I don't have to use spacers when making adjustments on the Delta. But that might not be long enough on my Mini ST2. I had about 2" sticking out on my Rover until I spun the stem back around to the front, Then I raised the stem to the top of the Delta riser.
I used this one. It is cheap. Quote from previous post:
So I got a 210 mm cheap stem extender from Amazon for about $20. That's about 8 inches. So I achieved a 4 inch drop.
https://amzn.to/3N3lyqYOnce you clamp it, you can remove the pre-tension screw on top and clamp your handlebar where you want. I, however, rearrange the spacers and tighten up the pretension screw afterwards and figure it is a second safety mechanism. Should the extender clamp fail, my handlebar would be somewhat held on by the pretension screw. You can do all this without removing the clamp of the stem extender.
You can buy a shorter one. It depends on your needs. I was not sure so I got the longest one.
Naturally, the more expensive stem extenders make it easier - because you don't have to rearrange spacers and pretension screws while adjusting height (I am assuming - never actually used an expensive one). But it is also twice as expensive and when I started out I wasn't sure it would work.
I like it. I think 45 inches off the ground is too high for a handlebar - especially off road.
You assume your own risk and use your own judgment doing this.
I am still testing and I am not sure how this will work long-term although I am impressed with the crash performance when I crashed. It seems to be good enough around the neighborhood and riding on the trails and off road on groomed grass near where I live. The land is full of rabbit holes and hidden ditches. I need to ride slower but the stem seems to hold up rabbit holes and all and my previous higher speed.
I would not know what to do, for example, if I sign up for an expensive bike vacation. What if the stem fails at the start of vacation? I'll worry about it when or if that happens - no plans for a bike vacation.