I just bought a Rad Mini 4 and a Step Thru 2.  The ST, while in 7th year (and 6th to a lesser degree) shudders and vibrates severely.  The derailleur and the High/Low stops are correctly adjusted, and I get good shifts up and down in all gears. However, when the bike is in 7th gear, the chain vibrates severely and you can feel shuddering in the cranks and the bike.  You can sense it a little in 6th gear, but mostly in 7th gear.  The remaining gears are smooth.

Any ideas?  This does not occur in my Mini 4.

I'm having trouble locating a small frame bag where I can keep a set of bike tools, spare tube, etc. on a Mini 4 that does not have a rack.  An under seat bag would interfere with removing the battery.  I've tried a frame bag that attaches to the base of the handlebar stem with velcro, but the base of the stem turns with the handlebars.  Any ideas or recommendations that does not involve getting a rear rack?

I received my Rad Mini 4 yesterday, and noticed the derailleur on the bike is a "Mezzu MicroShift" and not the Shimano Altus that the bike is advertised to have.  Anyone else experiencing substituted components?  I'm sure it is a sourcing issue, but I'm a bit bummed.  It's a pretty clunky and loud derailleur.  My wife heard me shifting gears and asked, "is something wrong with the bike?".