[linux-lvm] Resising underlying array

[georges.giralt at free.fr]

Hello 
I've an old server which use software raid and lvm (Debian based). 
It is made on a set of 3 320 GB Sata disks. 
The system is build on a couple of software mirror (3 legged): md0 is at start of disk, 200 MB size, used for /boot.
md1 is made with the remainder of the disk space and is set up as a 3 legged mirror which is the sole pv of the volume group onto which the system is built.
200 MB for /boot was sensible years ago but now is a joke. So I plan to extend these 3 partitions up to a couple of GB. And of course reduce by the same amount the 3 remaining partitions making md1.
The volume group is far from using all PE in the PV, so I hope I will be able to reduce the PV size without harm. But I'm unable to decide on a workflow and loosing data or downtime are not acceptable options... 
So I'm begging your help on a suitable workflow to make this happen.
Many thanks in advance ! 
P.S. the 3 disk are here from a time when the system was set up using mirroring into the LVM... Time long gone.