Nobody uses pgrens other than for shrecks for obvious reasons. Simply being ok in performance, but high cost is something nobody wants to deal with.I don´t build PGs any longer. Simply because LMG Grens are more cost effective and easier to use. Keeping an LMG Gren in cover is better than running in with valuable PGs that cost you an arm and a leg to reinforce.
The double Schreck upgrade is meh. A Pak does a better job, the ammo is better spent on LMGs and mines and most of the time you will end up giving Schrecks to the enemy, simply because 3 entities get wiped on a regular basis.