A smoke system with tank can run around 12 oz empty... might get by with 8 using a TME or something like it... Though ths plane would take smoke no problem and still fly nicely, I wouldn't add 12 oz plus 12 oz of smoke... That's 1.5 extra lbs on takeoff...
Post a pic of your tail setup and radio setup... there's GOT to something not quite right to be that far back.
Get the CG more forward before you concern yourself with the trimming... CG can play havoc on how a plane reacts...