My initial thoughts would be to carefully remove the rust by soaking in coke/similar. Then cleaning, drying, and carefully add some sort of rust preventative like jenolite* the just ride it and keep an eye on it.
You could carefully add a clear coat ontop if you wanted, but how often is the underside of the top tube going to get wet and grimy?
the gel verson will be easier for this. You should also be very careful about getting it on other paint work as it may distort the colour. But overlapping the white base coat should be ok.
My initial thoughts would be to carefully remove the rust by soaking in coke/similar. Then cleaning, drying, and carefully add some sort of rust preventative like jenolite* the just ride it and keep an eye on it.
You could carefully add a clear coat ontop if you wanted, but how often is the underside of the top tube going to get wet and grimy?