The Hotchkis boxed subframe connectors were my first overall modification I ever did for my Camaro way back in the day
Did I feel anything? I'm not really sure. I added these on way back when I didn't know $hit about modifying my car. Didn't matter.. I still had the crappy stock shocks. Basically swaybars, springs, shocks have a lot of effect on handling. Compared to those, subframe connectors have almost no effect on handling.
They do make good jackpoints though. I jack the whole side of my car up 1-2 feet from the middle of the SFCs without any problem.