Originally Posted by
barba
It places a great deal of stress on the steerer tube. Failure would be the concern, and it would no doubt cause a nasty crash.
If you need that many spacer and a high rise stem your frame is probably the wrong size for you.
+1
In a few cases with very large riders I've had to search our vendors for very tall stems, especially when a stock-sized frame isn't quite enough.
I can see that the OP is using an adjustable stem, my guess is for more bar height. My preference is to use a riser bar rather than overextending the steerer for those looking for more bar height. With the fight between riders wanting lighter bikes and thinner steerer tubes, there's not much material there left to support the bars, especially when extended past 40mm. Also, using relatively weak carbon spacers adds nothing for support.
Look into a tall city bar, or perhaps a comfort bike if you still feel you are uncomfortable.