I fiddled around for ages before finding the best aero position, it will take ages but when you've
got it you feel great, beleive me, and it does save time:-
1. Get the normal bike position correct first. this is a must.
2. Put the tribars on in a position that you think is right, ride it and see how it feels. If you
feel uncomfortable after 20km this ain't right, make biggish adjustments here.
3. Keep cycling with them in this position, cos when you get it right you'll feel so much more
comfortable.
4. Don't worry about keeping a flat back - it won't make any difference if you are a rookie, you'll
save more time if you are comfy than if can't keep going in the aero position. Focus on Comfort,
I looked at photos of Indurain and Armstrong doing their TT's - I couldn't see a flat back there.
5. Adjust only one setting per ride and only by a max of 5mm.
6. When you've got it right scratch the position on the seat post and saddle rails and tribars.
OR
go to a pro bike fitting shop and get the job done properly
Take your time
Good luck
Cow Parsley Man