I personally have tried it from the left hand side but find that rather awkward as a matter of fact.... I do it from the right side and the only problems I have encountered is from leaky pump nozzles.... I always use some of the paper that is provided by most if not all servos here to wad over the tip of the nozzle as I insert it into the tank opening and while taking it out as well, problem fixed.
I find that by turning the bars almost all the way to the left, there is no hassle really that can not be overcome by just a little diligence on my part.
I will say though, that I do agree with the comments of it could have been designed a bit better as far as the opening angle. And now I think on it, the old Ultra I had had a big round cover that flipped up and then one opened the screw cap, the same kind I have on my car. That huge cap thing opened up backwards as well and I do not recollect ever complaining about that either....
As to using the ness cap thingy, or others for that matter, unless they were lockable I wouldn't pay 5 cents for one, let alone the exorbitant price they want for them..... And if they were, it would mean carrying another key as well....
Gramps....