Hi Don
OK fair enough, I would just provide this quote from
http://en.wikipedia.org/wiki/Landing_Vehicle_Tracked
"The LVT were used for logistic support at Guadalcanal, but their first real test was in the assault on Tarawa. Of 125 vehicles used, only 35 remained operational by the end of the day."
suggesting that unarmoured versions were in fact pretty easy to 'sink', and
"As a result of Tarawa experience, standardized armor kits were provided for the LVTs employed in contested landings"
showing that the unarmoured versions were relegated to cargo carrying because of this,
Lastly dont forget the armoured versions still should have there rear armour changed from 2 to 1 ie the back door is unarmoured and there carrying capacity dropped from 24 to 18.
best regards Chuck