I'd love to learn about the root you took. Currently the 217AH of AGM I have is working quite well other than heavy and taking up a ton of Space. Is there anywhere i can read about that same route you took or where I can look at purchased products?Sure, if that was the case. It's not though. While the Gyll battery is great value, $1500 USD for 5.1kwh is nowhere near as good as $600USD for 3.7kwh. It's just about twice the price per kwh ($294 vs $162).
When it comes to "smaller and lighter with higher capacity", I don't see how that's possible when we are taking about the same battery chemistry. With minor variances depending on the exact construction of the enclosure, the energy density is going to be fairly similar across the board.