How much quill stem insertion required?

[RockiMtn]

what do you mean by one/multi piece? aren't most if not all quill stems multi piece???

so in the case of my Brodie stem on the Sovereign, i could go half way?

 

[jamswinna]

Most stems out there are made with more than one piece of tubing, but some are forged/machined or extruded down from stock, such as sakae. Most are for road use…but there are positive rise ones around that iv'e seen on Miyata & other early japanese mtb's.
As for Paul's stem…i'd run it halfway or lower for serious mtb use, that way you'll reduce the risk of ever bending the stem…especially after the investment you've put into it.