S’mae Pawb?
Listening to Ysbyty Brynaber in the car this morning, they introduced the past tense of dylwn i. I would have said dylwn i 'di dweud rhywbeth arall, but the programme suggested dylwn i fod 'di dweud rhywbeth arall. Whilst the latter may be right, am I safe to assume that my version can also be heard in the wild?
Hwyl,
Stu
Yup 
‘bod wedi’ is certainly the ‘right’ way, but hey, people are lazy…
Diolch Aran 
I was told off if the strongest possible terms once for leaving the bod out - because it ‘didn’t make sense without’, apparently. Although this episode led me always to remember to put the bod in, so in a way I’m grateful, I’m also pleased to learn that the person who was just a little be rude to me and my Welsh was being an absolutist idiot and that what I had been saying up to then was also fine.
Being a bit dense here perhaps, but how is the “bod” actually functioning in this case?
i.e. literally, “I should that have said …”?
or something else?
Literally I should be after saying… - which is why it doesn’t literally make sense without, though as we well know here, logically making sense is not in any way a prerequisite for a functioning, living language. 
[quote=“robbruce, post:6, topic:2515”] I should be after saying …
[/quote]
Which is how an old Irish friend used to say it in English.
Thanks Rob. That makes sense now. So in the simpler “wedi” constructions we learn earlier in the SSiW lessons, e.g. “Dw i wedi yfed” means something like
“I am after drinking”, and the “to be” verb is in the “dw i”.
Whereas " dylwn i" just means “I should”, with no version of “to be” attached to it, so needs a verb to follow, which could be something completely unrelated to “to be”, like “mynd” (or actually “fynd”), or in the case in question, could be “bod”, to make the “I should have …” = “I should be after …”.
Interesting stuff.
On a slightly related note, we have learned mi fedra i for “I can/am able to/will be able to”, ayyb; what about the past tense for this, that is “I could”. I am aware of gallwn i, but wondered if the equivalent using *medru" rather than gallu, would be mi fedrwn i, or if there is another pattern in this case?
Hwyl,
Stu
Wel, mi fedra i ateb fyng nghwestiwn fy hun!
medrwn i
medret ti
medrai fo
medrai hi
medren ni
medrech chi
medren nhw
As a supplementary question, though, are these heard often in the wild, or is the form using gallu more common yn y Gogledd?
Hwyl,
Stu
Yes. But please, please don’t over-think it - it will get in the way of producing all of those natural Welsh sentences that come out of your mouth naturally and without apparent thought.
Agreed 
The thought was prompted again by Brynaber banging on about gallwn i… Currently, I am quite happy with o’n i’n medru.
Hwyl,
Stu
This came up for me recently when I was staying in Y Bala. I noticed my hostess, a first language Cymraes, would use ‘gallwn i’ often when expressing ‘I could’ and once I asked her if you could use medru the same way and she said no, it would be the wrong tense. But then a few days later I was expressing confusion about when to use gallu as opposed to medru and she said something like well, they mean the same thing. And I responded by asking “except you don’t use medru in the past tense” and she said 'you can, that would be medrwn i." So I came away thinking that perhaps medrwn i is grammatically correct (Gareth King says it is) but not used that often. I’m pretty sure I have heard it used on s4c. I suspect that there is a difference in meaning that I am not able to understand, at least at this point. 
No, I don’t think there is, it’s just a matter of personal preference (and first language speakers getting tied up in tangles when someone asks them to explain a point of grammar!)
yeah, I was wondering if that might be the case, thanks Aran.