Thanks all.
One of my reasons for asking these later questioms is just plain curiosty--the need to learn!
Secondly, there is a lot of good 3dm files stuff about and I have been quite happy in importing a lot of it into Carrara in the past.

Thanks for that Carrara import setting advice

For those with Carrara.
Michaels suggestion to move the angle in the Carrara 3dm dropdown to 3 did increase the number of polys and lessened but did not cure the problem as earlier reported.
OBJ, 3DS and lwo seem to be the better imports into Carrara from MoI---I obviously can confirm!

Brian