First questions; I have a GE Box with 200 amp service. I have one sub panel and need to add 2 more. Is there a limit on how many sub panels that can be added? My home has gas heat and gas water and therefore total current is not a problem. Second question; My existing GE panel has horizontal blades for most of the breakers except the bottom row where they have a combo horizontal and smaller vertical that allow the THQP 1/2 size breakers. It would be nice to just change a few of the single horizontal blades to the combo units so I can plug in a few more 1/2 size breakers. But they have the anti-tamper screws holding the little bars on. So I assume changing the little bars would exceed some code or breaker box limit. Thanks Jeff

There is no limit to the amount of subpanels.

Yes, there is a limit to a maximum of 42 circuits in any one panel, hence the tamper proof screws that will not allow any more circuits to be added to that panel, along with any field changes or modifications to the panel will violate it's UL listing.