Hi David
I have no great problem with the Eye Relief afforded by these two (4mm & 6mm) eps. The beauty of the barlow is that the ER stays the same. You guessed it though. At these magnifications, anything viewed through a plossl ep just scoots through the narrow fov. Not a great drama, you just get a lot of practice at nudging your Dob.
I'd love to have a bo peep through a super wide fov ep like a Nagler at these focal lengths.
I have on order a Narrow Band Pass filter from DGM optics in the USA in the 1.25" configuration. However, now that I have a decent 2" Barlow, I am leaning towards another 2" GSO SV ep - the 42mm, for DSO hunting; especially for planetary nebs. If the DGM NBP filter proves its worth, I may get its big brother as well.
I find I really like the 'spacewalk' feeling I get from these budget priced eps. They're big bazookas (especialy combined with the UO 2" Barlow), and in that regard, not everyone's cup of tea. But I like 'em. I might think differntly if I had heaps to spend
Cheers