As far as I can gather from the wiki the configurable option for ram and I would also presume space is an override (eg. if selected use that value instead of the plan value).
If this is the case it would mean I would need to create a configurable options for every plan.
If I could set the configurable options as an addition (eg. plan is 1024mb ram, configurable option is +1024mb ram for a total 2048mb ram) then I would be able to create one set of configurable options for each platform type regardless of the number of plans.
If I am wrong and it already works this way great (then my suggestion would be clarify the wiki) elsewise that is my suggestion.