The second variant was the "Swift F Mk 2", of which 16 were built. This was practically the same as the earlier F 1, except for being fitted with two extra ADENs and the leading edge of the wing being altered from straight to a compound sweep configuration. However, the addition of these cannon caused problems as the structural modifications required to house the increased ammunition load led to dangerous handling problems with the aircraft and it was clear that more thrust was required from its engine. Numerous further modifications were then required to resolve the issues.