Just a suggestion, but I think if you modified the Flex ATX mounting cage to take either a Flex ATX power supply or a pair of HDPlex 160W/300W AC-DC units you'd have a significantly more appealing unit. I was amongst the first to get my hands on the FSP 500W 80-Plus gold close to three years ago (after pretending I ran a serious PC development company to get a sample lol). It was so loud that I ended up just giving it away to iFreilicht who was super into Flex ATX at the time. Additionally I wouldn't even consider myself a sound Nazi like a lot of people here.
Along these same lines, I think one of the things you perhaps haven't considered in your design is that while the big gap in the front will be great for letting air in, it will also be awesome at letting noise out. I foresee the sound from the 40mm fan channeling through the Flex chassis and puking out right where the glass and metal are furthest apart. If you're using the case correctly with the glass facing you so you can see your 1500 dollar GTX 1070, odds are the fan noise will be reaching your ears virtually unobstructed.
I think the other thing to consider is allowing for a push/pull fan configuration whereby you can intake air with a 60mm fan in the bottom right corner and exhaust out the top, again using 60mm fans. The advantage here would be significant airflow across the motherboard and particularly the area around the heatsink. I think if you had this implemented properly you could have a max supported cooler height of 40ish mm and keep your tempered glass side panel intact.
Hey Craig, great seeing you here! First, thanks again for all your private feedback before reveal
To be honest, I never had a Flex-ATX before, so I didn't know it was so loud lol.
I wonder how those custom psus from Geeek will end up like, we will order one of them to test if this is a possible solution (read my last post before this). Adding HDPLEX as an option ( but not the only option) is indeed a possibility we are considering, as it would easily fit in the current layout, and we would just have to add extra screw holes for it. So we may test this, thanks for the advice.
About the bottom right fans you suggested, I'm not really sure it would do much for the whole airflow, as its air intake would be all sucked by the GPU. It might be good for gpu temps, but maybe not much for cpu. Also, we would have to enlarge the case a bit to make them fit there.
I don't know why, but since the start I put in my head that the best option is passive air intake and active outtake. Maybe its just the experience I had before with other types of air-cooled enclosures lol.
Cheers!