Agreed, WOK, the alterations are of minor technical complexity. The more imperative factor (put simply) involves the subtle interplay of the added weight (fixed to the frame) of these modifications--and how that weight in its respective positions will change the way that stress loads move (via resonant vibrations) through the airframe.
Those strains evidence themselves only after many cycles in operation. The frame may survive mathmatical projections and destuctive load-testing, but that doesn't necessarily mean you're ready to stamp it with the seal of approval.
[This message has been edited by Leanan Sidhe (edited 16 February 2001).]