I emailed BPI maybe a week ago asking if i could use my 120 grain pyrodex RS charge in loose powder, heres the response i got back.

We really recommend a maximum of 100 grains of loose powder.
Experience
has shown us that this is about all that will burn in a 26" barrel.
The
pellets burn much more efficiently. If you are looking for improved
performance at 150 yards, I would look into these 2 options depending
on
where you live and what kinds of bullets your game laws require.

1- If PowerBelts are available in your state, switch to the 295 grain
(for Deer) or 348 (for Elk). Use 150 grains of Pyrodex Pellets.

2- If you cannot use pellets in your state, switch to Triple Seven
loose
powder in the FFG grade. This powder produces slightly higher energies
than RS. Sight the gun in at 150 yards and you will only be a few
inches high at 100, a few low at 200. Use the same bullets as above.

Regards,

Mark
BPI

If i can use 150 grain load with the 348 powerbelts i should easily be able to go back to my charge of 120 grains loose with the 350 grain maxi hunters. I may start off at 100 grains and see how recoil is and then up it to 110 and so on.
So all of this "spanish junk cant shoot no more than 100 grains is total hog crap. They are limiting 100 grains loose powder due to them finding, anymore powder is a waste and wont burn complete. Man these guys TB and RW really spread false rumors about BPI. I thought the email got right down to business and answered my question and then some.