Long (very!) but really cool video that explains a lot of this:
@
chimaera - Man I really hate you for this (in a good way). The video is kick ass for noobs like myself - now I can see why you love the "cluster" over spreading them out evenly. It also explained a lot of stuff so I (think) I have it clear in my head at last.
Also somewhere in this thread some had linked to this heatsink -
http://www.ledgroupbuy.com/makersled-designer-heatsink-kit-professional-grade/
Whilst a little more expensive (looking at around $300 in total for a 8x2x2 + delivery) it does look very versatile, flexible and easy to use. I'm now thinking of build 3 "modules" (as I have 3 holes in my tank bracing as explained earlier). Each module with have 4 x 6" heatsink kits, drivers, etc all physically joined together.
Each Heat sink will have around 10-12 LED's - looking at the emulation of Radion -
http://makersled.com/?page_id=2#recipes - and dropping the greens. (meaning I will need 4 drivers (need to confirm each 1 driver can drive each string) per module.
So far I have (per module - note how each number divides by 4 so it can easily be converted to per heatsink)
12 x Cree XP-G Cool White
12 x Cree XP_E Blue
16 x Cree XP-E Royal Blue
4 x Osram Oslon SSL Hyper Red
(Just to add confusion I might swap 3 x Osram Oslon SSL Hyper Red out for some True Violet which adds another driver, another channel to control, etc unless I just swap all the reds out for True Violet)
The controller can then control 3 drivers on each channel (1 per module) so all 4 colors can be controlled seperate to other colors, but consistently across each module.
Geez - I hope that make sense - it's clear in my head.
It's almost time to stop talking and start ordering.