Veg-Art

Got c4100 tonnes per year to fell for 5 years of unthinned 39 yo spruce block grade 15-18 in a remote island location but on reasonably good rising ground. We are thinking of doing it ourselves with an experienced operator using either a Valmet 860 or similar, or an excavator/tractor-trailer set up. Will chose depending on running costs/availability of spares etc. Interested to know say a per 1000m3 cost for operation and maintenance of either set-up other than labour. Expecting to be in the forest for 45-55 days a year and intending to fell whole tree for biomass fuel using boom fitted energy head and weigh device. Are the weigh devices accurate? Intending to load small boat but need a failsafe to check weighbridge return which is done elsewhere by others.