I am not sure that flowable silicone is right for sealing pouches.
The suggestions I have heard were for thinned down vacuum grease.
I have used it and it seems to work well without imparting stiffness.

It might be possible to thin the silicone sealant enough to not cause
stiffness.  I have heard (but not verified) that flowable silicone
is just thinned down regular stuff.  The stuff I have used is Dow 111
High Vacuum Grease, thinned a lot with acetone or MEK.  I would be
interested to hear from people who have used it to seal pouches.

Best regards,
Spencer Chase
Garberville, Calif.
http://www.spencerserolls.com/