EAA had 5 x C+'s, S/N's 474, 475, 476, round-dial and S/N's 497 & 521, IIDS machines. The first three a/c were relatively light and flew very well. The two IIDS machines were, IIRC, somewhat more troublesome at times (no idea why). I recall being told that IIDS became standard fit after a certain S/N, but stand to be corrected on whether or not that is factually correct.