Steve,
Yes, you can 'stitch' together your raster maps. The
trick is to have enough overlap of the map to provide
a nice edge to cut by using r.mapcalc.
I have used this technique with s.surf.tps deviding
the area up into two section. You do need a significant
amount of overlap but the results can be worth it
in time saved.
Hope this helps.
Kym M. Lenkus
DAVIDSON LABORATORY
Stevens Institute of Technology