I had the same problem when I was flying helicopters 15 years ago.... (not anymore however
) I had a weighted sandbag that went underseat of a robbie and sometimes I used another in the other seat for ballance.
For the Jet & Longranger I used divers weights under the seat cushion (I know, I know... dumb move looking back at it). Even with the weights the Longranger with full fuel and no pax got very close to the aft c of g and required a lot "LOT" of foward cyclic to remain neutral.
After that I dont think I have flown without another poler or pax up the front. Just remember that the seats are designed to collapse in the event of a high ROD impact so if you have to put anything under the seat.................
make sure it's blunt
