Racecourse stable limits will only become an issue if the divided race gets 24 declared and splits into two 12 runner races.
At that point,there are provisions within the rules that can be employed if necessary to get CH into his race.
Firstly:
The BHA shall reassess Field Size Limits and adjust them if necessary:
after Closing, or after Confirmation of Entries for Early Closers; and
after the deadline for Declarations to Run.
Secondly:
A series of clauses that define which races will have runners eliminated, with the BHA setting a priority order. And also a clause that states divided races will be the first to have runners removed.
Plenty enough loopholes available if needed. And the CH race has already been given the number one spot in the priority order, so it will be the last race to have runners removed because of stable limits.