I make single, double and triple-tier Elektron stands in acrylic. Plenty of happy customers on here. They all include ventilation holes to accommodate the A4 and all of my designs are able to be used 'upside down' to give you two different mounting angles, tall or shallow(er).
For example, the 3rd and 4th pictures in the gallery below show my 3-tier design in both tall and shallow orientation.
Pictures at the bottom here:
http://marmotaudio.co.uk/galleries/