OK, thanks.
As I read it, you want to be over the Channel by late afternoon or early evening on Sunday 22 June, staying in (for example only) St Omer. This means:
Monday 23 June, leave St Omer, to ride to Switzerland, returning to Calais, seven days later, to arrive in the late afternoon or early evening of Sunday 29 June. Over this seven day period you want to include the Stelvio pass at some point. You want to avoid motorways, if possible.
As a very basic starter, the Stelvio pass is at the very eastern lower edge of Switzerland. From St Omer to the Stelvio pass, reasonably direct but avoiding motorways, is about 1,000 kilometres / 620 miles. Over two days, that is 310 miles a day.
View attachment 412008
Is that doable? Yes, I guess so, if you crack on. Two days out of seven gone, five left.
If we assume that it’s two days to return to Calais, that leaves three days to ‘do Switzerland’, which (very roughly) is the area bordered by the red hand drawn line:
View attachment 412009
Doable? In theory yes.
As Calais and the Chunnel is your return destination, I’d suggest that you’d need to find yourself somewhere around Basel on the evening of Friday, 27 June. Then, over the next two days, you’d take non-motorway roads to ride (roughly) in the direction of this yellow line:
View attachment 412010
That is, very roughly, 800 kilometres / 500 miles, over two days ie. 250 miles a day. Doable? Yes, I guess so.
Comment:
1. You could of course reverse it.
2. Does this look doable to you?
3. If the answer to comment 2, is yes. Then fill in your chosen routes in the red bordered area, allowing yourself three days.
Your turn now…..
PS I have all the routes of the linked site in post #2 available.in GPX files.