Balloonet For varilift

Suppose   our  envelopes   had  a  balloonet system  that  when  pressurized  would   force lift gas   out of  the envelope     and into  a  a tank   under  slight pressure  (  or in some way  decrease  the gases  volume  )  to  produce   a slight  HTA condition   .  
   The  balloonet  poses  a  way  to   pneumatically  move a large  area  of gas , under  slight pressure   .  like  an  air ride  air bag  can lift   heavy  objects .  Suppose  our   air bag  was  a heavy  gage  bag  able to   take   5 psi   and the gas   envelope   could  take   7  psi .  Would  that  be   enough  to   change  from  LTA to HTA  ?   with  a volume of  say  a cubic yard   of gas   at  5 psi  ?   With  a given  that  we would  be   slightly   LTA   at  full envelope volume.

Maybe if you just used a ballonet to add superpressure to the main envelope. Any mass added to the ballonet. Would weigh down the airship. I remain skeptical of using tanks.

Yes, tanks are very heavy, however, some fabrics can withstand thousands of psi, which I don't quite comprehend those ratings, however such a bag itself, say 4 foot in diameter and 20 feet long could hold 100 psi of helium that would be 250 cubic feet and at 100 psi you would have an additional 1750 cubic feet.  This would be a supply for a larger ship, of course, but it could be scaled down to size or pressurized to what ever amount you think might be needed.   At 14.7 psi at sea level, if we take a given amount of air and compress it to half it's volume it would register 14.7 if I am right, so 7 psi would be 3/4 ths the volume and result in 75% of the initial lift.  You would be very heavy with just that much compression and fall out of the sky.  So even two or three psi would result in significant buoyancy change.   The outer shell envelope for a small ship should be able to handle that if it has ripstop nylon.   Anybody?

Interesting    on  both posts  ,  So   lets  say   you  use  a heavy  , safe and  cheep  balloonet  gas Co2 ,  and  give  the balloonet   volume  its  Most  weight potential  ,  And also  allow   the  Lift  gas  to   be  pushed out  of  the lift  equation into  a heavy  bag  under slight pressure . The bag  weight   should equal  to ,  or be   slightly  more  than  the  Lift gas  inserted in its volume  could lift .