I got this reply in the Protools Post Forum, and I thought I’d share it with everyone here:
best way to do this is with an external clock, a sync i/o and engage .1% pull down. you can also use a USD.
another “down and dirty” way, if you don’t have the above is :
create a new 23.97 (or 29.97) 48k session. import the 24fps tracks and apply SRC to them. for SOURCE SR select 47952Hz as your source. this will pull it down (make it longer) to 48000.