Sorry I missed this. I have been slammed for the last few months.
I would recommend leaving the instal size at full. The Zendrum is the only instrument that can really grab all of those velocities. If you must go down a level, try making up for it by using the Vel -> Amp feature.
My "gig rig" only has what I need for a gig. No need to have all 1tb of data! I use that in the studio.
Another thing to point out is the difference in pack sizes. My packs are not as large as stock and Platinum Samples. I focus on getting the velocity range correct for the playing response. Going fro Large to Med will not loose that many samples, but it may knock out some important velocities. The installer just does some math and grabs the correct amount.