I'm working with upto 100mm thick modelling board and you'll find the kress limiting for long bit choices required to reach the depth your looking at. Really you need 12mm+ shanks for the longer cutters. I use 160mm long cutters with 14mm x 100mm flutes and a 12mm shank. Be warned that these are expensive for carbide although you can pick up HSS for a lot less.

If it were me I'd swap the kress for something that will take at least an ER20 collet like 2.2kw chinese spindle.