Raise the bottom and lower the top. It should slow down the wood speed. Another option build a wood create out of pallets with wheels on it. Then you wont have to use the wheel barrow or stack it
I have a similar set-up only my wood stairs were obviously made by a severely drunk fellah so it was an easy choice to just rip em out. I built a couple big boxes, put HD casters on and roll em empty into the Bilco... toss down wood... and roll full boxes into the basement next to the stove. Good nuff ...
Do the whoop-de-doos in the slide make the wood go flying in random directions, or take weird bounces?
Yup part of the cure is to lower the top side of the slide and raise the low end of the slide. I also think the tread mill idea is a pretty good one, way easier than trying to toss thru the window hole. Might want to keep the speed down on it so it doesn't toss the wood out thru the window on the other side. Al
This method adds one more time picking up the wood but the energy saved from going up and down the stairs is worth it. Much faster. I have done 3 trailer loads in the time it used to take me to do one.