GRMA, a Shéamuis. Is cuimhin liom gur chuala mé "idir dhá stól" áit éigin cheana froisin ach ní raibh mé in ann a fhianaise a fháil amach ar a' bpointe.


"In two minds" is the standard English form (SOED). "Of two minds" is the standard American form.

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Múinteoir Gaeilge - Irish Teacher
My "specialty" is Connemara Irish, particularly Cois Fhairrge dialect, but I can also speak Ulster and Munster Irish with native-level pronunciation.
Is fearr Gaeilge ḃriste ná Béarla cliste, cinnte, aċ i ḃfad níos fearr aríst í Gaeilge ḃinn ḃeo na nGaeltaċtaí.
Gaeilge Chonnacht (GC), go háraid Gaeilge Chois Fhairrge (GCF), Gaeilic Uladh (GU), Gaelainn na Mumhan (GM), agus Gaeilge an Chaighdeáin Oifigiúil (CO).

idir dhá stól reminds me of the English phrase 'falling between two stools'.

I would have heard idir dhá cheann na meá before too in the same context as the English phrase '(hanging) in the balance' e.g. Tá cinniúint an chine dhaonna idir dhá cheann na meá.

I've got to say that idir dhá aigne sounds suspiciously like the English idiom translated (almost) directly too. Idir dhá chomhairle is one that I've heard or read very often, and is therefore the one I'd use.