Content in buffer chests is ignored.

I only have this working for trains currently.

For that to work you have to supply the signal "Activate Request from Buffer Mode" to the trainstop.

What I think I can do for cars / tank / spidertron, is add a 2nd module that enable request from buffer chests if in the equipment grid.

that sounds good imo 2 seperate modules since they are 1x1 anyhow, the one u already have with req/active and another with buffer/active

Please try the new verion 0.4.0 ..

Hold the module in your hand and press "R" to change it toggle it between normal and buffer mode.

i dont know if it was prior to the 4.0 update or not, but if the spider now has no (zero blue) request slots it will not empty its inventory with the trash slot

That's been the behavior since the start. At least one slot in the inventory needs to be filtered before the logic activates