By "Peli" - Do you mean a Pelicase?
If so the answer is very simple
Four drilled holes with small "case feet" positioned to position the case on the rack
Then a couple of good quality velcro cinch straps (Mine are 50mm x 92 cm) and nothing will move it!
Otherwise these straps will secure most things to a rack. Two running across the rack and one along the line of the bike makes things immoveable
If so the answer is very simple
Four drilled holes with small "case feet" positioned to position the case on the rack
Then a couple of good quality velcro cinch straps (Mine are 50mm x 92 cm) and nothing will move it!
Otherwise these straps will secure most things to a rack. Two running across the rack and one along the line of the bike makes things immoveable