I'm not to sure about this special order. I just picked up an 05 bighit that the shop gave me a decent deal on, and there is more than enough room to accommodate a piggyback....you could hide a damn football in there, so unless something drastic changed from the 05's, I wouldn't worry about it.
If you do end up ordering in a shock, and it doesn't fit, you can always send er back.
P.S. I've currently got a Van RC on the bike, and the piggyback has more than enough room.
well i know for a fact an aftermarket dhx 5.0 will fit on a 06 big hit. friend got one for his big hit last season and has no problem at all putting it on there. the piggyback on marzocchi roco shocks do tend to sit a little farther from the shock body however.