Hi everyone, so there are some verbs that end in a slender consonant in some tense forms - 2nd person imperatives and 3rd person past tense (or all past tense forms when scartha, probably), but otherwise the verb root is broad.

As examples I think siúil and tochais do this as well as all those 1st conjugation syncopating verbs (codail, ceangail etc.)
e.g. siúil: shiúil sé but shiúlaimíd, siúlann sé, bhí sé ag siúl and so on.

I've been working through Teach Yourself Irish 1951 and there's only small mention of this in the 2nd footnote on page 114:

I'm wondering if anyone knows of another grammar resource that expands on this wrt Munster Irish?
Or if not, is there an easy way to identify these types of verbs (outside of the syncopating ones)?

Not some verbs ...
I’d say, most polysyllabic verbs (including those polysyllabic only in spelling or in pre-reform spelling, e.g. siubhail -> siúil) belong here.

Polysyllabic verbs that are broad in imperative are rather exceptions, e.g. gearán.
Verbs that do not become broad before endings are exceptions, too, e.g. tiomáin, comhair
Syncopating verbs like deighil with a slender middle consonant don’t become broad (deighleann), of course.

Thanks Labhrás!