Working out observations from the night of 27-28 April 2022, this topic came to mind as it did to me, too, at the eyepiece that night.

Another very flat one: MCG+04-29-060 (PGC39432, UGC7321). It was mentioned before on this forum in this post: https://www.deepskyforum.com/showthr...ull=1#post4111

mcg+04-29-060.jpg

getjpeg.jpg

Here it is in Aladin.

NED gives it a dimension of 6.74 x 0.43 minutes of arc. That's a ratio of 15.7.

For the galaxy that was the subject of this topic, MCG+07-30-011 (Holmberg 643A, Zwicky I 88, PGC51503, UGC9242), NED states 5.69 x 0.36. A ratio of 15.8.

So it's a very close second!

This is what I observed using my 14" SCT @ 168x / 29':

A very faint but clearly extremely elongated line (can't call it a streak), even in brightness, at the limit of visibility without AV. With AV subtly brighter west of the middle in a central part that is elongated in the same direction.
To the east, in line with the galaxy, is a mag. 13.5 star.

Give this one a go, too, next spring!