sorry for the late reply I was outside my office for several days.
With the data you sent me I got the folowing results of expected deflection:
Icosit KV 340/45: 0,7 mm - 0,8 mm
Icist KC 340/65: 0,4 mm - 0,5 mm
In general both products are suitable , Icosit KC 340/45 will have a bit better vibro insulating properties.
Kind Regards