I encourage a difference of opinion as I am relitivly new to the class..
Here is my reasons for the change.
I have found old mossies popping up here and there but they can be too heavy to be competetive especially for myself at 100kgs.
The old rule min of 65kg was changed to 55kg making these older boats slightly disadvataged. I have lost 4 kg from dropping my center beam and 4 kg from my heavy decking giving me half a chance at reaching min weight with an old boat. Cant see why the optional main beam would cause any issue as most boats these days are all under weight with a main beam an unless I am mistaken it has no bearing on a boats performance. Your spinniker sloop rig boat may put more of a thorn in the idea but I intend to race Cat rig.
If I don't like my changes it wont be hard to install the beam...