On my R25 (Classic) I've mounted a magazine holder and attached to the lower portion of it I attached a 4 hole cup holder. This was immediately above the dinette table on port side between the two windows. The thickness in this area was about 3/16" to 1/4" as I recall.
I had no choice but to bolt the Magazine rack to the bulkhead (cabin wall) with thru bolts. The protruding bolt was secured with SS washer and round-headed nut along with sealant for water proofing. I had to file the bolt length so that the washer with the round-head nut would screw down securely and not bottom out into the round-head nut. The R-25 (Classic) does not have the inner teak lining that the newer boats have so I had to go through the cabin wall.
I'm confused as to why Kenny has advised you do your modification on the starboard side, but this could be that I'm not familiar with the R25SC's layout on that side. You did say you wanted the condiment rack near the dining table, right ?