I think I have flown 4 different PA-25, all glider tugs. I don't remember any of them smelling of chemicals. Maybe the smell dissipates faster in the hot and mostly dry SW USA where I flew them.
Light stick forces in a PA-25?? Not any I flew but I was spending most of my flight hours racing standard class gliders so I suppose it's all relative.
Back to the accident - Has anyone seen a preliminary report yet?