VISUAL INHERITANCE SUCKS, PERIOD!
I've had many headaches working with this crap, it's so annoying! VS is so buggy when you wanna inherit something yeah everything shows up fine in the compiled app, but not at design time. I recommend you give up, because it causes more headaches

I had written about 2000 lines of code for 6 forms and then I found out that I had to rewrite them cuz this stupid inheritance wouldnt work well for designing