I think the extra fibreglass in the enclosure surely helps suppress midrange reflections back though the 2235H.
When I heard John's 4435's in Boulder I was quite surprised by the midrange, smooth and no woofer overhang usually attributed to large driver covering the midrange.
Quite a nifty design actually although I undeniably prefer the 2123H with the 2344a horn after the Robert Hamell audition at Long Island NY, but thats the beauty of diy JBL, roll your own.
Ian