4 and 5mm EP recommendations

I am looking for a good high power eyepiece for my optically excellent 8" F6 Newt. Radians are out -- cost is an issue. I have a Klee barlow which seems to work OK with a 12.5mm ortho, but I have nothing to compare it too and wonder if a 4mm ep would give a better image. I will probably also be replacing a 6mm Celestron ortho that seems to be mediocre.

I don't really care too much about eye relief I never hear anyone mention this when it comes to eye relief, but the real problem for me is bumping the scope because the eye relief is so small (I have an light scope). The 6mm ortho that is completely fine as far as eye relief.

The UO orthos are an obvious choice, but I am not sure if I should get the HD or the regular since I have found that volcano tops give one a feeling of more eye relief. What do people think of the new shape?

What else:

Ultrascopics 5 and 3.8

Ultima 5mm -- I have the 7.5 and love it, but I would bet I need to stick my eyeball right up to the 5mm, but still it should give great image brightness and contrast. Anyone using this one successfully?

Ultima barlow -- the 2.8 power from the Klee means that one ends up looking for some odd EP focal lengths to get a certain magnification -- 2x would be more useful. Or I could use an 18mm with extension tubes on the Klee.

So... I guess it's kind of a UO HD versus classic ortho versus Ultima 5 element versus Ultrascopic 7 element versus
something with a barlow question. OK?

I've not tried the UO 5mm HD, but in general I
do not like the new flat top design. I've used
the normal UO 5mm with the volcano top, and it is good.
Eyerelief is tight, but quite useable.

Ultrascopics below 7.5mm have a built-in
2x Barlow. The 5mm Ultrascopic is just the 10mm
with the added 2x internal Barlow. The 3.8mm is just
the 7.5 with the same 2x internal Barlow.
So eyerelief is not too bad.

I think the 5mm Ultima does not have the Barlow
(i.e. will have very short eyerelief). Otherwise
the Ultima and Ultrascopic series are nearly identical.

There's a 5 mm Tak ortho for sale on Astromart right now. I don't think you can find a better eyepiece for high power.