Oh Boy, well we will start with a big IF.
1. IF your ignition is just a bit on the low side then the 6v will be the answer and you will have no problems.
2. IF you ignition has a component that is failing, the 6v is a crutch. You ignition will start the act the same as it did on 4.8v even though you are on 6v. If this the case you will have some warning and should toss the ignition if it starts to give problems on 6v