i read and hear lotsa different opinions on hill style longbow riser woods and mass weight.
there is a camp that believes in lighter weight woods such as the myrtle genus can provide, and others are into heavy hardwoods like cocobolo and all the ebony flavors from around the globe.
given the dimensions and all the materials, save for the riser, are equal, and given the small footprint of a hill riser, ain't gonna be much mass bow weight difference 'tween lightweight myrtle and super dense lignum-vitae, just a few ounces, and yer bowhand ain't gonna feel that to any major degree.
so, personally, none of that matters a hoot to me for performance - it's really all about the bow design, the limbs, and how you use it all best to your advantage.
ymmv.