Hey there! Here to say another 6MT conversion was successfully completed on the Canadian side! Maybe this post will help those looking for a newer updated part list and procedure.
Here are the parts I used:
Reverse Shift Piece 24240-PNS-000
Mainshaft 6th Gear 23590-RAS-A00
Needle Bearing (35 x 41 x 24) 91103-RAS-003
Collar (28 x 35 x 24) 23916-PNS-000
Countershaft 6th Gear 23491-RAS-000
My Element did not have a welded reverse shift piece so I drove out the roll pin and simply slid on the new one (there was no place for a roll pin to drive back in, this is okay).
Some info to clarify about the 5-6 Synchro Sleeve set; I did not purchase it banking on the fact that I would be able to flip the 5-6 Synchro Hub. I had thought of this before reading another person had tried this and thought it was brilliant! There is a downside to this though. There are little detents in the grooves of the hub that help keep from popping out of gear (from factory these are facing the 5th gear). By flipping it to face 6th gear, you risk popping out of 5th. To also clear some confusion, the only reason this conversion is possible is because there's a synchronizer cone ring (the brass ring) on the 6th gear side of the sleeve set. When you take it apart you'll see it fits onto the 'angular' spacer between the sleeve set and the bearing on the end of the shaft.
After a stout 2000km road trip across Maine, I can say the 6th gear is holding up perfectly. 5th gear will only 'pop' out when you put it under a lot of load (going up steep hills or accelerating hard to get onto highway). It will not pop when under light load like casually accelerating up to speed or even downshifting into 5th under the same circumstances. This can be overcome though if you hold the shifter (not with all of your force, just enough to stop it).
You do not need to buy the 'special bolt' - you can reuse it and it torques to around 86 ft-lb (left hand thread). Make sure to remove the lock out cam for reverse otherwise you'll have trouble shifting into 6th. I also modified the slot to allow for reverse in it's "new" position by 6mm.
When you are reassembling the transmission, the snap ring in the case that goes onto the countershaft can be hard to seat. I did some research and basically it requires you to 'drop' the transmission on the ground. Sounds scary, but if you put some wood under the open end where the clutch would go (about 2-3" worth) and pivot the transmission on the wood - you can gently tap the other end of the case on the ground to seat the countershaft snap ring (you might be able to set it in place, open around the groove but it won't seat until you hear it click into place). Just a heads up!
My fuel mileage gas increased from 10L/100km to about 7.5L/100km.
I've attached some pictures to help explain some of these details!
Cheers from Canada! More to come about my Element soon!