IS PENN SON OF NETHAWC MERELY A CORRUPTION OF RUN SON OF NWYTHON?

My main concern at this juncture is Rachel Bromwich's suggestion that Penn son of Nethawc (my new candidate for Uther Pen, father of Arthur) may merely be a corruption of Run son of Nwython.  The only way for me to know whether this was possible was to consult the actual MS. containing 'Culhwch ac Olwen', viz. THE RED BOOK OF HERGEST.  So that's what I did!

817 for Run son of Nwython
837c for Penn son of Nethawc

https://digital.bodleian.ox.ac.uk/inquire/Discover/Search/#/?p=c+0,t+,rsrs+0,rsps+10,fa+,so+ox%3Asort%5Easc,scids+,pid+9bf187bf-f862-4453-bc4f-851f6d3948af,vi+b704febf-c9c4-4f23-8312-cb7cd67ef6c6

http://www.rhyddiaithganoloesol.caerdydd.ac.uk/en/ms-page.php?ms=Jesus111&page=200v

What follows are the two screen saves of the names as they are found in the MS. itself.

While this kind of thing always requires a subjective judgment, to my eye Run is not at all likely to have been corrupted into Penn.  But, then again, I'm not a trained paleographer. Dr. Simon Rodway of The University of Wales is such, and when I told him that I didn't think these two names were even close, he replied only with "I agree."

It is still my contention that Penn son of Nethawc, a warrior serving under Gwythyr in C&O, is Uther Pen, who fights with Gwythyr in the 'Marwnat Vthyr Pen.'   And Nethawc is simply a pet-name for Nwython/Neithon.

I've now had word from Dr. Simon Rodway of The University of Wales that he agrees with the author of the following study when it comes to the name Pen[n] son of Nethawc of the MABINOGION tale "Culhwch and Olwen."

https://openaccess.leidenuniv.nl/bitstream/handle/1887/40632/05.pdf?sequence=8

I've pasted the relevant section from the study below.  But suffice it to say that I have no reason to doubt at this point that the Pen son of Nethawc (= Nwython/Nechton/Neithon/Neidaon) who fought with Gwythyr against Gwyn for Creiddylad is the same as the Uther Pen who fought alongside Gwythyr in the MARWNAT VTHYR PEN poem. 

We also need to remember that Rachel Bromwich and D. Simon Evans make the following comment on the name Penn (in the English edition of CO, published in 1992; information courtesy Will Parker via personal correspondence):

"Penn uab Nethawc: some element appears here to be lacking. Pen(n) is itself an unlikely personal name."

They say this because Penn looks to be an epithet.  And that is because, in all likelihood, the name Uther has dropped out, perhaps precisely because it was mistaken for an adjective.