NeilJ

Generally, you should not add panels with nominal power more than 120% of the rated power of the inverter (for Voltronic Axperts). The reason is that the control algorithm is poor, and overshoots are common. More than 20% more than the control algorithm is expecting can damage your battery and cause various problems.
This 24 V model has an exceptionally weak solar charger (600 W). Connect it to a maximum total of about 720 W of panels (hard with today's giant panels), and if you need more solar power, add an external MPPT that connects directly to the battery. Use a type where you can set the absorb and float voltages, and set them slightly (about 0.1 V) lower than the same setting on the inverter. You have to be a bit careful not to charge the battery with too much current, though with only 600 W from the inverter's built-in solar charger, it's not too hard.
I note that there are other 24 V models (usually with "PLUS" in the name) that have a much more powerful built-in solar charger.

im Sure he means you can install them as (2p2s) (or is it 2S2P)
 
but yes, what he means is you will install two panels in series, and connect those two series panels in parallel. 
you can read my comment from earlier, you cant exceed the VOC. putting two in series will exceed the max VOC. 
to save on cabling, connections and mountings - and in general panel costs. just install 2 larger panels (2x350w) in parallel. 
or just buy 1 x 650w and get it over with. thats what im going to do. 1 x 6xxW panel, and it makes it rather easy to add another in future when i expand. realistically, calculate your solar needs during the day. and go from there. 

You can ad 600 Watt of panels. 2 x 300Watt panels.
The max VOC of the mppt is 75volt. If the total volts of 2 panels exceeds 75v you will have to connect them in parallel. 
You can exceed the panel wattage safely by 10%
 

I'm not sure if it works from the APP, but if you have an installer code via the website, then use the image below to set the fan speeds.  It is found under the main heading of MAINTAIN.
I think the first fan speed is the general speed of the fan for cooling / standard inverting, whilst the 2nd one is the speed under higher loads / inverting.
Hope this helps!

Very nice install.  Here is 1 of my recent, tight fit Lux installs... in a broom cupboard in the scullery.  Got the client to knock out all his shelves and stuff to make space.
1 x Lux SNA5000 with Hubble AM-2
May I ask some questions please?
1)  For some reason, my Lux installs are showing my 100ah batteries as 50ah (Shoto & Hubbles)... is there a setting or something on the Lux that we're missing?  Cable maybe?
2) Did you adjust fan speeds for an inside install?  Default is 70%... I turned down to 50%... and is pretty decent.
3) Being a solar installation, how have you gone about doing the SSEG?  The Lux SNA5000 is an unregistered inverter, in City of Cape Town anyway, so it won't pass the SSEG application?
Your feedback / guidance will help a lot.

Consolidating anything to do with Shoto batteries under 1 topic, for easy referencing / problem solving.

Not that i have registered because i have no panels, but my research was very clear that an off grid inverter will never be on that list as those are grid ties, and you do need to register them but as off grid in a much lighter weight process

Very nice install.  Here is 1 of my recent, tight fit Lux installs... in a broom cupboard in the scullery.  Got the client to knock out all his shelves and stuff to make space.
1 x Lux SNA5000 with Hubble AM-2
May I ask some questions please?
1)  For some reason, my Lux installs are showing my 100ah batteries as 50ah (Shoto & Hubbles)... is there a setting or something on the Lux that we're missing?  Cable maybe?
2) Did you adjust fan speeds for an inside install?  Default is 70%... I turned down to 50%... and is pretty decent.
3) Being a solar installation, how have you gone about doing the SSEG?  The Lux SNA5000 is an unregistered inverter, in City of Cape Town anyway, so it won't pass the SSEG application?
Your feedback / guidance will help a lot.