Hi Adam
My experience of plotting diamond grade has always been on flatbed plotters not drum. We use a Zund fitted with an ultrasonic edge sealing head (blade).
DG is 430 micron thick so even a 1 meter length will have some weight about it so that alone would be a big consideration as the liner is synthetic and shiny which may cause slippage, also as the thick vinyl threaded backwards and forwards over the drum the thick cut vinyl may "ping" backwards and could snag and catch.
The manufactures are constantly updating and developing these pieces of kit so if they are saying it can be done great but I’d suggest having a demo
Summa have their Flatbed Summa F series which was launched earlier this year and I’m sure that plots DG but I have no idea if it has the facility to edge seal the DG after plotting.
The simplest way to explain reflectivity grades is-
Class ref 1 = is glass beaded (enclosed lens) or easier still the level of reflectivity on a car number plate (not sure about Israel)
Class ref 2= has a honey comb finish (encapsulated lens)
The difficulty faced with reflective vinyls on the highway is that a cars headlights shine and bounce back on a roadsign at a different height and angle to that of a trucks so then came the next generation of reflectivity being-
Prismatic = full cubed (prismatic lens) better known as Diamond Grade,
and a favourite for both traffic signage and emergency vehicles because no matter what angle or height the the sign or vehicle is approached at the reflectivity level is not reduced.
Hope this helps a little
Gill