Here's Owen Bell's web page on increasing useful load:
http://www.aviationenterprises.us/us...dincrease.html
Based on that web page, one mod type increases useful load by 350 lbs to a gross weight of 5120 lbs and another one increases it by 390 lbs. Both incorporate a fuel jettison system.
For more info, contact Owen at 615.865.1802 or
owen.bell@juno.com
Ernie