Still getting around to doing my LRPS, mostly as Bath is a long way away and I'm trying to get a friend up to standard to do hers
Re no bigger than A4 - that was a definite as told to me by the Yorkshire Region Director who I met for advice, the argument being it 'hides' what could be deemed to be problems in larger prints !!!
10x8" was suggested as the norm - but for me that's a crop I don't like, and on an Assessment Day I attended as guest, most were A4 (and most passed btw)
Glossy seems like a no-no to me due to reflections, remember when first shown the Panel has to sit as a composition in its own right, if part of it can't be seen properly without the judge bobbing & weaving about due to reflections its not going to help your cause
Dave