Line work 500d/d/e/f
The 500 series is a great machine due to it small MR disc dimension, excellent visibility for pilot and sensitive (but not over sensitive) control. It also has a relatively short tailboom and thus not as prone to momentary weathercocking with wind gusts.
This makes it a very stable platform for this type of work, as for using a E model or indeed an F model there is no benefit, with the kind of payload used in this role neither a more powerful engine or indeed as in the f model a beefed up main transmission is of any use.
For line work the D model is fine and it's lower fuel consumption gives a much better loiter time and lower running costs.