Deco X20

Just installed the above 3unit pack (main plus 2 satellites) and looking now to add more units,
do I buy another three pack and add those as satellites ?

Does network performance drop if I have to have one satellite work through another?

im within the 5000sq ft area but the fibre terminates in one part of the building so the Main deco is located there, plugged in, so in effect loosing some of its coverage.  
Any better way of achieving coverage?

thanks.