[LAU] time stretch in Ardour4

[fred]

Hi list,

have made some samples to build a new song, and I like to decrease the 
tempo a few.
Is it a way to time stretch regions *on a numeric basis*?
Meant, the time stretch graphical mode is ok, but samples in this case 
are of different sizes (some 4 bars, some shorter)
and I can't find a way to strech all of them keeping tempo equal between 
each of they.

Thanks,

-- 
Fred,