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Geoff, it would definitely be nicer to use a more compact 1.25" barlow, esp. with tiny orthos and plossls. They look pretty ridiculous in the 2" barlow. Your Celestron Ultima might be a lot better than Orion's version of that barlow.
My Shorty-plus did poorly with all my EPs: panoptic, nagler, Stratus, GS & TV plossls and UO HDs. It was worst with the wide FOV EPs and the TV plossl. There was a yellow discolouration around the edge of the field, in the last 4-5 degrees (so about 8-10 degrees total). This did not occur with the HD orthos, which have the narrowest FOV, 45 degrees.
Excessive light scatter was evident with all EPs, as was internal reflections on bright objects. Actually, this was the case early on when I only had GS plossls. Then the good people of iis were saying it's my crummy EPs: "Put good EPs in the barlow and it will perform well." Then I got the Nagler & the Pan, but I found the same problems when using these EPs. I only found the performance acceptable with the HD orthos. But I'd still get better contrast and no false colour with the UO 2". BTW, the Shorty plus is meant to be an apo, but I'd still get false colour off planets when not centred in the FOV.
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