Possible upgrade of inverter

I currently have a Gen1 3.6 Hybrid single phase GE inverter, but in reality it's only able to manage around 2.5kwh, it can be frustrating at times, such as the other night when exporting to Axle energy, I could only export 1kwh as had the Aircon running and the house was using around 1.5kwh.
What are my options to changing the inverter, I've seen a gen 1 5kwh one for sale on eBay, but will this make a difference and also how complex will it be to change, is this an installer thing or something I can do myself?

I have 4kwh max panels and a 9.5kwh battery (I'm also toying with the idea of adding an extra battery)

Appreciate people's thoughts and suggestions on what inverter could work, I think something that could cope with 3 - 5kwh actual capacity would work for me.

Cheers

Iguana I think with gen-1 the battery interface is limited to 2.6kW, so even a 5kW gen-1 can only export 2.6kW from battery alone.
Gen-3 has a 3.6kW battery interface. Not sure about gen-2.
Probably can't go up from 3.6 to 5 without DNO approval.

Probably best not spend too much money assuming Axle payments will remain as high.

Gen 2 is essentially the same performance as Gen 3. It's an installer job to change inverter. I don't know if it's currently possible to commission a new one. Used one might be OK, since it's already commissioned?

There wouldn't be much point in adding another 9.5 battery onto a gen1 inverter as you wouldn't be able to charge it fully in an off-peak window.

DD Probably can't go up from 3.6 to 5 without DNO approval.

You can't and I don't think they'll issue a G99 for defunct equipment anyway.

Avenir
I think charging 2x9.5 with a Gen1 is just about possible if using Eco7. (7hrs @2.5kW= 17.5kWhr), assuming that at min there is minimum of say 5% charge. 18.05kWhr needed from 5% to 100%
Tight I know, but I am trying to convince myself it will be OK for me if i can find a reasonably priced 9.5

I'm looking only at second hand only, feels like gen 2 could work, but don't see any second hand at a cheap price yet.
Only made £1.40 with axle last night, perhaps I may just have to accept this and stuck with the one I've got