you can actually go below 0.0152 interp
http://i.imgur.com/TCoh4qd.png
^ screenshot taken in firepowered MGE for convenience sake, but I haven't seen my interp go above 0.1 in months
im currently using these rates
cl_cmdrate 100
cl_interp 0.01
cl_interp_ratio 1
cl_lagcompensation 1
cl_pred_optimize 2
cl_smooth 0
cl_smoothtime 0.01
cl_updaterate 100
rate 80000
and despite servers being limited to 67 cmd/update rate, the server still shows that im at 0.01 interp despite console saying my cmd and updaterate have both been set to 67 by the server
I dont really understand why it happens, but this seems to be the lowest possible in tf2, as anything above 100 just doesnt work.