I just weighed some flight packs, the regular AA type come in at around 100 grams but the A type packs are about 140 so perhaps that will help, My motor by the way is quite well forward the cowl only overlaps the fuselage by 1/4", I understand theres an ammended distance to set motor at on Great Planes website but I needed to set mine forward for firewall clearance as its a fourstroke.