The OP will be visiting several countries on tour in Europe and hence the main destination may be vague.. it is applied when say a person is going to one particular place for 2 weeks and only 2-3 days in other places but this does not seem to be the case with the OP as he will be on a sightseeing tour..
The rule AFAIK is '
If you intend to visit several european countries and if you dont have a main destination or if you are going to spend equal number of nights in more than one schengen country, apply at the embassy or consulate which is your 1t point of entry..if visiting the schengen region and you have a clear main destination, apply in the embassy of tht country '

I myself hv applied and recd the Schengen visa multiple times based on the first POE rule..