Small and weird solar setup advice please!

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Apr 30, 2022
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Hi everyone nice to meet you. This might be a bit of a long one so bear with me.

My current setup is no solar, but a solax triple battery with about 13.5kwh usable capacity (from 17.4 stated which seems a bit crap but that's another post!). This is about equal to our daily usage give or take. It was installed by an MCS installer but is not set to export. I want to supplement with solar as I like the idea and want a bit more juice esp. to run AC in summer. Problem is my roof. I cant put anything on the top roof due to box dormer on the southerly aspects, but I have a wrap around extension on the ground floor. This faces about 125 degrees at the back and 215 on the side, which abuts the pavement as we are end of terrace.

After a bunch of research, here's what I plan but here's my questions. I have a Solax x1 hybrid 5kw hybrid inverter which is dual string capable, can limit export, and according to the spec sheet has 125-550V MMPT range and start input voltage of 85V. Nominal voltage quoted at 360V.
Q1: I assume that those figures are per string, as apposed to total of both strings? Same for startup voltage?

BACK ROOF 125deg - approx 12 degree slope.
I have 3 velux windows in its span, which means the usable space is approx 3 lots of 125cm wide (to be touching the velux frames and overhanging the flashings) by 200 high.
So the best I can do on this is 3 panels - I'm thinking the Perlight 400W delta blacks because 1) they're black 2) the dimensions make the most of the gap, being 1140 x 1646. I believe I need to add 25mm each side for mounting, which would leave me clear of the velux frames. They also seem to have a relatively high Voc of 49V, which I think I need to have a shot at the MMPT range and even the start input. Q2: Am I missing anything?

This gets the sun from first thing. This time of year, the sloped section where the panels would be, starts to get shaded by the building at around 3pm but this shading only affects two of the panels due to the wrap around.
Q3: Once the two panels shade, I am well below MPPT and start voltage, but there will be one panel still in sun - will this damage it as the current has nowhere to go? What happens?

SIDE ROOF 215deg 12 degree slope.
I could fit more panels on this roof and it is arguably better, but I'm concerned that as it is basically a single storey extension right onto the pavement, it will be too easy a target for people to try and get up on the roof, and even if I fit security bolts and they can't nick, they'll make a right mess in the process. Q4: Thoughts or am I just being a wuss?

Q4 - given the fairly shallow inclination and 90 degree relative direction difference, could I get away with putting the panels on both rooves on a single string, perhaps with some Tygo optimiser
s? Feels like if it did work it would keep things running much better, but is this just going to be a problem?

Q5 - Final question. I'm proposing to DIY as the SEG is just not worth the cost I believe that the currently very busy MCS installers would charge compared to such a small setup. Given all I'm doing is plugging in some panels into an already properly setup and tied hybrid inverter, any point trying to get the battery installer to certify?

Thanks everyone!