A buddy of mine who's a new electrician called and told me his wholesaler gave him a two tube slimline f96,f84,f72,t12 ballast ballast as single tube ballasts of this type were no longer produced so just cap the extra wire during the install.He did as directed and now this ballast is tripping the thermals every hour or so.i have never tried to swap ballast like this as i like to sleep at night.Being a nice guy I called around and found him a few at another wholesaler.My question and I see it all the time is that I will find an f40 ballast with say f20 tubes that seem to work.what problems do you guys see resulting from these types of mismatches? thanks