I imagine that you had to stand pretty hard on those peddles - and as you see we ran a scab line most times. Funny thing is, one of the long time operators that I chummed with recently had to have his hip joints replaced while he was only in his mid-50s. I suspect standing on those brakes all day must have worn him out. Asbestos in the brake linings must also have been delightful to breath all day - eventually they put air conditioning in the cabs to pressurize them and to keep the dust out.
Back in the mid 80's, I worked for a logger down here in Washington, Munn Logging out of Granite Falls. Munn specialized in long span, rough ground shows, almost always down hill. Munn had two machines when I worked there, a Tyee slackline machine with a Madill tube and a Madill 052 tension yarder.
We mostly used the Tyee on these long span jobs. On one job we had about 5000' of skyline out, running a "south-bend system" and side blocking as much as a thousand feet off the skyline. We were flying the logs over standing timber, a creek, more standing timber, and a road. We had so much lift that had to hang a piece of a ripper blade off a TD25 behind the fall block for weight just so we could get the rigging down. This weight was shaped like a tooth and we called it the toothache. We painted the toothache bright pink so that we could see it in the fog. We used to tie the back end of the yarder down on these downhill shows, but quit doing that when we bent the tube over in the middle one time. It was quite a sight to watch the back end of that machine come up off the ground when there was a big turn hanging on the skyline. The tracks would lift up five or six feet sometimes. I asked the engineer if it bothered him and he said not really. It bothered him more when the tube got pulled down.
I worked a few times under the Madill 052, again in downhill shows. Contract logger has posted pictures of what is left of this machine on the Madill thread. We never used the slack-pulling carriage, we always ran a Grabinski with butt-rigging. People found it hard to believe when I told them that were running a Grabinski out 3500' and yarding downhill. That machine would fly a big turn of logs fully suspended all the way. Quite a sight. The only thing I did not like about working on that machine was the size of the rigging we used. 24" blocks for tail blocks. On steep ground we'd make a haywire layout just to move those blocks and straps sometimes.