CAA Paper 98002 gives a lot of useful information about helideck friction and testing in addition to the information to CAP 437. It's surprising how poorly aluminium helidecks perform in terms of friction.
CAA Presentation on Helideck Friction
The last 3 ships I inspected all had Frictape nets fitted. These provide the required 0.65 coefficient of friction, have a low profile (and thus a lower tripping hazard for helideck crew and passengers) and a much longer life than rope nets, particularly in tropical climates. The last vessel I checked also had Frictape deck-edge safety nets.
Frictape helideck landing nets