sc,
I don't think one can make any assumptions about the COD basement one way or the other. Recall that TGT was once considered to be a basement target [H] and that analogies were drawn with STT on 15-1 for H, E and COD prospects. Have we now got something at COD which is structurally a TGT lookalike? I don't know - and they probably don't either!
At one point, of course, COD [based on the old knackered pre PSDM seismic] was thought to be closer to 750mn bbls mean expected.....so the short answer is that the only way to pin figures down is to have some positive result from drilling [and if it fails it's academic anyway!]
I'm always suspicious of 100mn target figures. TGT was also 100mn in terms of its pre-drill estimate [ie pre TGT-1X].
Peter is right re the big picture.
The rig choice is simply one of practicality - and the optimum targeting for the basement may well be in a different location anyway.