Aligning Scope on Tomahawk

[gunnstack]

Hope you can give me some assistance here.  I bought the .177 calibre Tomahawk a few months ago with the scope set up at the shop. ( no tools just eyeballed in).  No problems initially but then the scope started turning in the rings.  I realigned to where I thought the crosshairs were in line with the barrel but I have a feeling it's not quite right.  The trouble is there are no flat spots on the breach/barrel where you can sit a bubble level.  The only way I could find a level area was to break the barrel and sit the level on the end of the stock and another level on the scope and adjust the scope accordingly.  The problem is I am relying on the stock being on the same plane as the barrel and perfectly true but I don't think this is neccessarily the case.  I thought of having a piece of Alminium machined to a finger push over the flats on the barrel where it breaks from the breach and going from there.   Anyone out there who can give a simple fix on this problem.  I have a suspicion that the scope is not really up to the job (Deben Hawke HD) but other than alignment seems OK so far.
Thenks for any assistance.

[doc_kreipke]

I notice that B-Square makes a level that attaches right to the scope rails. Seems to me that would be about as accurate as you could get. I don't have one but have been thinking about buying one. Anybody have experience with this item? Other companies besides B-Sq make them?

It might be kind of expensive to get one to adjust just one scope, but if you think you'll be aligning a number of scopes in the future, it might be worth the investment.