One last thing to consider with respect to safety. In addition to the multiple warnings above, consider that adding a resistor of any value will make your oven easily capable of reaching temperatures well above the autoignition temperature of most anything you will put it in. Don’t do this, it is not smart. If you choose not to listen and do it anyway, have a fire extinguisher handy.
While I like to see people who know what they're doing attempt these hacks, because I think it adds to the knowledge base in such as way that, eventually, less saavy DIYers might get a better sense of direction... at this point, no offense, but I don't think this is for anyone that's asking questions.
I come from two generations of electricians and have studied ovens for countless hours, and I wouldn't go near this. At least, not at this point.
If you've got an electric oven, chances are very high that it both has a broiler and will hit 550. If it can do both, 1/2" steel plate will get you 2.5 minute NY bakes in a manner that won't ever burn your house down, and, while steel won't give you Neapolitan bake times, if you're only going to 650, it doesn't sound like Neapolitan is your goal.
Even if Neapolitan is the goal, I don't think this answer. Being able to increase the temperature of the oven, at will, is far secondary to broiler strength when it comes to Neapolitan. Either you've got a freakishly hot broiler and you can do NP, or you don't and you can't. If the broiler is close, this might push it over the top, but I wouldn't attempt this first- or, as I said before, ever, if I wasn't 110% comfortable.