Scale is always a hot potato when it comes to Gerry Anderson's plethora of vehicles. SWORD is no exception and Wotan and I discussed this very subject during his recent beam-up to Moonbase. There are many ways to approach the subject - SOLO strip, TV21 illustrations, the SWORD Annual, the Manual, the box art and/or the toys themselves.
Thunderbirds fans have already had a go at cracking the scale nut and above is one in metres that appears on Wikimedia [Nigel Sadler 2009]. Nigel appears to have used the Carlton toys of the early 1990's - agreed? Interestingly for me, being a Thunderbirds scale novice, TB5 is HUGE compared to the rest of the fleet with TB3 a close second. There is another more stylised version in feet on Deviant Art [harnois 75].
The subject of scale is one that Wotan and I will return to soon but this will hopefully whet the appetite of reader Bill E, with whom we recently chinwagged about this very thing. Any SWORD scale theories/ methods/ attempts you may have gratefully received!