Another option might be to fit one of the 6 hp Chonda motors for the cutting and use the Honda just to run the alternator. Would take a bit of work to setup but the 6 hp Chondas are very light so would not add a lot of weight to it. The 6 hp motors are $160 +postage Another alternative would be to fit a horizontal shaft motor to run the alternator, probably easier to mount that a horizontal shaft.
http://www.ebay.com.au/itm/6-5hp-MOTOR-4-STROKE-STATIONARY-ENGINE-HORIZONTAL-SHAFT-WATER-PUMP-GENERATOR-5-5-/250906055739?hash=item3a6b2a943b:m:mqs-haCcuOsKJcG-hB1NGkg

Another thought is a bigger battery so it has power in reserve for climbing the hill and hopefully it would be able to build up some charge when going down the hill because it is not working so hard.
I think you could probably slow the alternator down, I'm not sure but I think they would reach max volts output at probably 3000 rpm

Last edited by NormK; 03/05/16 08:46 AM.