similar but not quite ;-)
i'm in the process of building a drum riser for my room (they're currently sitting on carpet on concrete, blech) and i'm going with 8x8 square for a couple reasons.
first, my main kit seems about the same size as rimshot's, 7 piece pearl export, 20in kick, 14in snare, 10, 12, 13, 14 mounted and 2x 16 floor (one on under hihat on left). handful of cymbals stands (6-8 depending on day), couple mounted tom stands, cowbell rack, throne, etc. i will be adding a set of chimes and an 8in mounted soon enough, and the kit currently measures 6x7......so, room for expansion is reason #1.
secondly, i'm sure there will be times when a drummer with a monster double-kick kit comes in and the 8x8 will come in handy. of course, between my exports and my mid-60's ludwigs, i've got most of the timbral bases covered, but sure, whatever.
third, and the most motivating factor--plywood comes in 4x8 sheets, and using 2 of those straight as they come greatly increases the "laziness factor".

besides, who really enjoys ripping 4x8 sheets down to 3x7 anyway? blech. 8x8 wins for "job simplicity".
i figure i'll make the supports out of 4x4's cut to 10 or12" high, prolly 10" at this point--room's only 8ft high, and strategically place them around the 4x8. i'll leave a 1" reveal around the perimeter so i can put some 8in or 12in planks around the facade and dress it up a little. definitely want to use a nice looking wood for that, and prolly the whole thing....maybe a maple ply or a mahogany ply if i can find it around here somewhere. not to hijack your thread, but if any of you've made drum risers in the past, got any "do's and don't's" you might care to share in addition to kicking out the real estate your kit sucks down?
cliff's notes: my kit, with stands, elbow room and all, will definitely take up 8x8.
cheers,
wade