Posted 06 April 2012 - 08:58 PM
i havnt replaced a roof myself, but i did have to make a huge section of one to add into the stretch mini limo i built. however a friend of mine has replaced a full roof, including a short section of the posts, and the technique was the same for both really.
get some lengths of box, or angle, or whatever you have readily available, and brace the posts up in as many places as possible. then cut the roof off at the top of the posts.
with some carefull cutting and measuring splice the new posts together with the old ones. ideally you need to do this in such a way that the cut/weld is staggered. i.e dont just cut through in one linear shot, the b-posts in particular have a definate inner and outer pressing which can be staggered by an inch or so. doing this greatly increases the strength of the joins.
having said that though, if your welding is any good, you should be confident enough to trust that your welding is strong enough with one linear cut on each post. if your welding isnt so hot, defiantely stagger the joins, and if you welding is pretty poor, get someone else to do it!