I would suggest that the committee members read the report of Quebec's chief electoral officer from December 2007 regarding a compensatory mixed system. This report includes a summary which I have here in front of me. You should have the official document. This report will provide a lot of answers to the technical questions you are asking.
In Quebec, if we had followed the chief electoral officer's advice and the terms of the draft bill, instead of having 125 ridings in which a member was elected in a first past the post system, we would have had 75 or 77 such ridings and 50 regional ridings. There would have been 50 regional representatives. Instead of having a single list for the whole province, we could have had between 12 and 15 regional ridings. That means that, in certain regional ridings, the list could have been longer, depending on riding size. We could also have tried to balance the 12 or 15 regional ridings to give more or less the same weight to voters and to the regions.
So there are different types of mixed compensatory systems, as Quebec's chief electoral officer stated. In other words, you don't have to reinvent the wheel. Academics and officials in Canada, including the Chief Electoral Officer, have devoted a lot of study to these issues. The Chief Electoral Officer produced a substantial report after a year of non-partisan study of the issue. You should draw on that, especially if you might develop a compromise or consensus based on that model.