There's a technique or two for feedin WTC's with a crane that are relatively safe IMO.
Tail tied limbs n logs can be lowered vertically until an inch or so over the feed table, then a groundie pushes it off COG towards the rollers, as the CO gently spools down, and the groundie bails prior to feed wheel contact with branch/log.
The drawbacks are the feed table being subjected to such heavy pick loads, even briefly, bowing them outta square. I know I've had to reinforce 3-4 BC1800 feed tables due to vertical off COG crane feeding.
The preferred technique's of course mid tied limbs n log feeding, but it's often impractical working in tight quarters!
Personally I'd go whole hog n buy the hydraulic feed arm for it, where the operator's behind a steel mesh cage!
Jomo