Also all Tameside wards are much smaller than Stockport wards thus I would think the balance of population is in Stockport.
Having nothing better to do on a quiet Sunday afternoon, I've just crunched the numbers for the populations of the four Hyde wards in Tameside and the four wards in the Bredbury, Romiley and Marple areas of Stockport.
The population of Hyde is 46,233. The population of those areas of Stockport is 51,418. That splits the population of the proposed new constituency roughly 53% Stockport, to 47% Hyde. (NB this is the total population, not the electorate - i.e. it includes children).
With 10 Labour councillors, 7 Lib Dem and 6 Tory, assuming people vote the same way in national elections as they do in local ones (yes, I know you can't necessarily assume that, but bear with me!), this does suggest it could be an interesting contest. Superficially Labour would seem to be favourites, but of course that depends largely on whether the Parliamentary Labour Party gets it act together (don't hold your breath!).