superdiy

Yes, they suggest that the minimum is 200Ah, because if you are thinking about it, if you draw full load from the inverter @ 4000W and 48V you draw 83 amps from the battery bank (losses ignored) - how long would a smallish battery bank be able to sustain that?
 
The 5KVA Axpert can charge the batteries at 60A via solar and 60A via utility and combine the two to 120A - it is recommended to charge the batteries at C10, thus you can effectively add a 1200Ah battery bank and still charge it without a problem. You may even add a bigger bank, but you'll have to manage it and ensure that you can keep the bank charged or not partially charge it and use it on a regular basis - here I'm not referring to the odd rainy day, but rather to daily cycling.

Finally 
 
Looks great!  Yes, I think the fuses blew because of the initial capacitor charge up - should have used the bulb method. 
 
About the smell, my infini did the same, but after a few days the smell was gone.
 
I can't remember, but I think you have the 5KVA model - 63A fuses might blow frequently if you have frequent high loads. The Axpert manual mentions 87A typical and to prevent "nuisance blowing" keep the following in mind: The current rating of a fuse is typically derated 25% for operation at 25