Roof Rack setup

I've just purchased a new hobie quest (3.96m long) and am picking it up either today or tomorrow. I drive a Mitsubishi Magna wagon and am getting some (removable) Thule roof racks fitted today. They are the solid bar type and they have a removable fitting system which attaches above both doors (about 1m apart). My question or issue is are the roof racks going to be far enough apart? With 1m between the racks, there will be about 1.5m of kayak hanging over each end. There is an option of moving the back rack back further on the roof but this would then have to be pop rivetted in place and wouldn't be removable. I really don't want to do this but do you think I will have to to support the yak? Another option was also to have the 2 racks over the doors and removable and then just have a piece of moulded high density foam further back on the roof as a third support.

All ideas and advice would be much appreciated.

Cheers.