Hi IC Gulf,
What do your loops look like now? Any straights in the middle of the end curves?
How long are the straights lengthwise?
I tried some loops in SCARM software... I am thinking that the Comet would have to be the innermost or outermost train if you were running O and the STD Comet at the same time - visually- the smaller trains on the outside and the Comet on the innermost loop would look the best to my eye.
That is 3 O trains and 1 STD train running at the same time.