If the Super Skybolt is within 10% of scale, it'd be legal (2nd one down): http://www.execulink.com/~gca/sub/aircraft.htm

Same deal for the 260 of course, although I've never seen or heard of the scale deviation being checked or protested at a contest.

You posted the wingspan... there is no rule in IMAC regarding the size of the aircraft (although it's a common misconception).

Hope this helps,
Baron Johnson