Before I became anal about tires and had the money to buy new, I use to repaire MANY sidewall issues over the years.. cars, jeeps, and bike tires..
patches hold well for road use IMO.. the high pressure helps hold them in place...
scuff, cement, and patch from the inside works well..
but lower PSI needs to be sewn as well..
some off road tire kits have thread to sew the rubber as well.. works a lot better..
new tires work the best