[Brizn]

Numbness / pain in wrists while riding. Could this be a result of having recently installed a stem that's about 20-25mm longer than my previous one??

 

[kaboose]

Could this be a result of having recently installed a stem that's about 20-25mm longer than my previous one??

probably. give your wrists a rest then ride again with the previous stem and see if the pain returns.
a stem one inch longer than the other is quite a big difference. when making changes, try making them in smaller increments.
K

 

[Caffeine Powered]

Could be. I'll try not to sound like my wife when I ask this but... how strong is your "core"? She's always doing yoga and pilates while I'm doing sit-ups and reverse sit-ups. Guess who has fewer back aches/pains... and she's 11 years older than I am. I've always tried to keep my abdomen strong and it helps reduce the pressure on my hands. It was obvious 4 years ago when a bad motorcycle crash broke both my wrists. 3 plates and 20 screws later my wrists are 100% of what they were pre-crash. By having a strong "core" my wrists were rarely under stress on the long road rides I did that following summer. So much so I was pulling my daughter in her trailer on 2-3 hour rides.

Unless you've changed your position to the point no amount of abdominal strength will reduce the pain you could be in need of some yoga. Which could be good for all of us.