The answer to your question is yes. Anytime the SFLSIZ value is greater than the SFLPAG value, it is considered an “expanding subfile”. Therefore there is really no good reason to make the SFLSIZ value more than (SFLPAG + 1). However, as I think again about it, there may be some memory allocation rules that apply but that is beyond the scope of your question.
Hope this helps.