Long time backpacker, the hammocking bug has bitten me!

Three questions: 1) I am 5’ 6” and 175 pounds, should I buy a top quilt that measures 66”? 2) looking hard at total Simply Light Designs purchase - Trail Lair and the synthetic 20 degree underquilt/tarp protector plus a synthetic top quilt of 30 degrees, will that combination fill my Olm 2.0 backpack to the brim or will they compress sufficiently? 3) Would I be better off with a down top quilt? Your advice appreciated, Butch.