If you search the international sites of makers like Echo, Husqvarna, etc., you will see backpack trimmer/brushcutters offered by these companies outside of the US market. So how would you feel about carrying the engine(a larger one with more fuel) on your back in an ergonomic sling and just have the weight of the trimmer shaft and head to deal with? Although I haven't seen this particular setup on the backpack models, some of the brushcutters in the same lines have pistolgrip controls to put your hand in a more natural position. If you could have the shaft and head weight only with the pistol grip control, perhaps some sort of arm rest/cup to use your forearm to steer(think how a metal detector is set up), would you choose a machine that you can one hand trim with, be able to walk forward while trimming without twisting your body and have more power at your disposal? Or is it all too monstrous for the job?