Great to hear about your progress, I would love to see some photo's at some point.
I am guessing you will be running the heat bed off 240VAC and connecting the 9 or 10 MK2 heat beds in series using their 24V connection points (pins 2 and 3), controlling them with the solid state relay?
This should work fine to generate the heat required but please be very careful how you set this up as they are not insulated and could easily short out to the heat bed causing it to go live if not earthed properly and possibly electrocuting someone.
What are you planning to use to insulate them from the aluminium heat bed (the material would need to safely insulate 240VAC but still conduct heat)?
Also I am guessing you will be earthing/grounding the aluminium heat bed for safety, just in case one of the MK2 heat beds contacts the aluminium heat bed plate?
Sorry for so many questions, but in giving you advice I feel responsible to make sure it's done safely.