Thanks Mudge, no I had not seen that. I find this a bit of a confusing topic because a document I found in the Air Force Museum of new Zealand states that both New Zealand and American documentation was referring to COMAIRSOLS as commander (replacing SENAV, Task Force 63 as commander of the Cactus Air Force that No. 3 Squadron RNZAF was part of) as early as January 1943, and definately in March 1943.
But everything I find in researching the internet states that Marc A. Mitscher was appointed COMAIRSOLS on 1 April 1943, and it seems to indicate he was the first such appointee.
I just found this page on Wiki which has a listing of COMAIRSOLS,
http://en.wikipedia.org/wiki/AirSols#Commanders listing them as:
RAdm. Marc A. Mitscher (USN): 1 April 1943.
Maj. Gen. Ralph J. Mitchell (USMC): 20 November 1943.
Lt. Gen. Hubert R. Harmon (USAAF): 15 March 1944.
Maj. Gen. Field Harris (USMC): 20 April 1944.
Maj. Gen. James T. Moore (USMC): 31 May 1944.
This list omits Nathan Twining who replaced Mitscher on 25 July 1943.
Regardless of that, it seems that COMAIRSOLS only came into being on 1st of April 1943, so I guess up till that point the commander in overall charge of the RNZAf squadron at Guadalcanal must still have been SENAV, Task Force 63; who up till March 31st would have still been Francis P. Mulcahy, I guess?