Flip the stem with caution

It lowers your front end, and every millimetre counts.

I recommend it and am looking at getting a shorter stem for my TT bike because I like being low and forward in the aero position. (I have already flipped it and removed the spacers)

But don't flip it just for looks... consider how you feel on your bike and what you are trying to achieve.

If you do flip it, try it out for a few days because it will feel different. If discomfort persists (and you may get discomfort, my partner rode his bike for over a month to get used to a higher seat and lower front end til it didn't hurt him) then change back.

Remember - all changes you make to your bike should be to enhance comfort and efficiency, and changes should be made in small ammounts, over time.