OK, sort of a fess up here.
In true school boy error or in true theory not meeting reality, having measured out the 200mm shock in place in the frame and its clearance of 60mm between the seat tube and the cross bar between the top stays, one would think with a 57mm stroke you should have 3mm clearance. I thought having seen Patdams photos I had better check by letting all the air out ( I had only let 50% of the air out due to the piggy back arrangement on the DH5, where its not recommended by Fox to work the shock without pressure in it ) and seeing fully the suspension in operation. Previously with some air in, the cross piece missed by about 3mm, tick, but was that true full deflection ?
View attachment 50017
Allas its not quite true. With all the air fully out and total movement, its not so.The cross piece rotates by about 15 degrees as it goes through the 150mm range at the back, reducing as it does the theoretical clearance of 3mm to about 0.5mm. Is that enough ? Yes and no, get some mud on there and its going to be compressed.
OK how do we give it more clearance, an offset bush in the shock will give about 3mm at each end
View attachment 50020
So if you insist on using your 200mm shock as you have one sitting around as I did, then yes you can use a 200mm shock as long as its max 57mm travel, but to give yourself true mud clearance, then fit either a single offset bush or one either end to give you back an extra 3-6 mm of length and thus clearance.
www.offsetbushings.com
Which leads nicely on to why I like the BB to be lower to terrafirma. I ride Whytes, love em, as they feel unlike virtually every other bike I have ridden, you are riding in the bike and not on the bike. Look at any Whyte and the ground clearance is always less than normal, its just one of their characteristics and once you have ridden one, its tough to ride a taller bike. Thus a shorter overall shock with comparative stroke, will give you a lower BB.