I am getting riser cables so that I dont run my gpus on the motherboard. I am using a cooler master case, a cheaper one than
this image but this will serve nicely to explain.
I have placed the case in a sleeping position and not standing as it is shown here. I now have 12 inch risers for my 2 gpus (R9 280X). Until I build something custom to hold the gpus, I was thinking of placing a plank on the case and placing the gpus flat with the fans blowing upwards. Will that cause problems or can the gpus be placed like that.
If by 'plank' you are indicating a wood plank then I would
not recommended that.
If 'plank' means a non-conductive, non-flammable substance in plank or rod shape then that should not be a problem. 3/4" PVC works nicely when secured so it does not roll. The GPUs are placed perpendicular to the support plank/rod.
http://i1273.photobucket.com/albums/y416/stumbling-orangutan/Fullscreencapture12192013104539AMbmp_zps6c325b49.jpgBlack box is case. Purple lines are support. Red boxes are GPUs.
If you have a plastic crate around, open air is my preference. (e.g.
https://bitcointalk.org/index.php?topic=163306.0)
