How Large can a QRD be?

Hello, I'm finally reaching the point in my studio where I'm DIYing my acoustic treatments. I wanted to use diffusion along my rear wall in the control room & was wondering what the size limits are to constructing a QRD Array. I was thinking of making a block of five 2' x 8' QRD diffusors to give me a 10' W x 8' H array. The wall in question is 15 feet wide x 12 feet tall. Total room dimensions are 15W x 20L x 12H Thanks in advance for your help. Jon

I cannot answer that directly, but DIY is my middle name! Google QRD using site:johnlsayers.com Brien D.I.Y. Holcombe