Mixing solar panels

Hope I don't confused anyone too much, I get muddled with all the numbers, I'm by no means proficient in this, so looking for advice.

I currently have 2 solar arrays. One is 2x325w 72 cell panels in series feeding a Victron 100/50 MPPT. Not planning on touching that one. The other array is a single 250w 60 cell panel feeding a separate Victron 100/30 MPPT. Current total wattage is 900w.

I have room on the roof for 1 more large panel that I was planning to wire in series with the single 250w panel. Ideally I would have preferred to avoid replacing the existing MPPT, but the max wattage for the 100/30 is 440w @ 12v. The unit is able to handle wattage above maximum, but it would be wasted (manual states "If more PV power is connected, the controller will limit input power.").

So here's the question - if I stick with the 250w panel and add another one in series, then am I correct in assuming that I should stick as closely to the rated amperage of the installed panel (8.24A) with any new one (i.e. no point in going to a 300w panel)?

The end objective is to add enough solar to reliably power a residential fridge and get off of propane. I have 600 A/H of LifePO4 (500 A/H usable). The primary consideration is not price (but is a secondary one), it is reliability of the system as we plan to leave the trailer at a remote location for extended periods and I don't necessarily want to worry about propane running out when we're away.

Thanks for your input.