[GRASSLIST:3856] Doubt about importin radar images

Hi all;
I' ve imported some radar images into GRASS.
The source are .png images and the four Lat/Lon coordinates of the corners, 
and my location is UTM projection European datum for Spain and Portugal.
So I've done the following:
First of all, I've done the conversion into my UTM projection with software 
GEOTRANS V2.2.4 of the four corners.

1) I've imported the png images
2) created a group and added all images to the group (i.group)
3) created a target in the destination UTM location (i.target)
4) executed i.points (marking the points and my GEOTRANS' calculated UTM 
coordinates)
5) executed i.rectify
It seems that the result is good. But (I recognize I lack enough background 
about projections...) I'm asking myself if  I've got a concept error:
 Perhaps I shouldn't transform the coordinates and should directly use 
i.target i.points and i.rectify to pass the images into a Lat/lon location, 
as the source images are, and later on to convert (I don't know how) the 
raster Lat/Lon maps into the UTM European1950 datum for Spain and Portugal?

Thanks and forgive me if this is too basic.

Best regards,

Javier