I don't know where you live, but if you ever want to sell you place and a private inspector or an employee of the title company find out that you have modified the structure from the original design without design documents and permits forget it.
I don't think that is wholly true. People modify from original structures everyday. As long as it done properly, there will be no problem with it.
An employee of a title company, most don't know which side of their *** to scratch if they have an itch, and an employee of a title company never checks out a house anyways. At least not around here. The only time any house or structure is checked is when someone buys it and request an inspection. Most inspectors do a walk through, hit the highlites and are out of there. When my son bought his place, the only thing the inspector was worried about was getting some heaters (baseboard ) in two of the upstairs rooms. He didn't give a **** that the bathroom floor was rotted out and the previous people could hit the toilet and piss and water were leaking through to the kitchen downstairs.
If a person was going to modify trusses while building a building, hardly anyone would have a problem with it. But modify one after they are up, and everyone goes into a frenzy. If people use common sense, and if they are capable of building a building their self, there is no reason that they can't modify something and it be structurally safe.
