I plan on shrouding most vents myself as well with 0.6mm black ABS plastic. Leaving only spaces open over the cpu fan and psu fan. Then adding foam rubber weatherstripping to seal the cpu fan to the case vent so it can only draw in cool exterior air. This lowers the cpu exhaust air temperature, lowering the temperature of case air. This also creates a very high pressure case that pushes warm air out any remaining holes (probably the side vents). It creates directed airflow that is forced to flow over the motherboard rather than recirculating indiscriminately within the case. This worked extremely well in my lian li pc q12 and Silverstone pt13b.
I would like very much to see before and after temps, if you've got 'em.
How does it wind up performing acoustically?