Meatbomber,
With Regard to the "line" of your jump run suggest you get an aerial of your DZ and plot vectors outward from the peas for the winds aloft forecast, this allows you to visualise the winds and their effects, depending on your GPS's capabilities if the winds are awkward consider an "offset" jump run, which I always find useful.
For example if the winds are howling out of the North on the surface but out of the West aloft a westerly jump run will yield slowest GS (obviously) but an offset to the north will have your jumpers opening upwind of the peas.
The more complex issue of the depth of the jump run is primarily a function of the number of groups on board and as such in the Skyvan or CASA can be a problem.
Without getting into all the various permutations I'll give you a few tips that have helped me out,
Winds aloft forecast below 20kts. have negligible effect on freefall drift derived from experience. So basically if your dealing with winds <20 put your jumpers out straight up or allowing for the inevitable flappin' about on the gate maybe .2 prior.
Also,if surface winds are <12 kts and/or depending on the peformance capabilities of the canopies you could can buy some "space" by putting them out even further downwind, thus allowing a larger area of "distribution"
The first jumpers out may not like this because they have to hold into wind but I usually tell them to take it up with the jumpers at the back who may take issue with being put out 2 miles from the DZ!
The arc method you mentioned works fine as well, only the jumpers don't like the tailgate moving about so you have to be ginger with inputs etc.
The biggest problem I had was jumpers ignoring exit separation (another science in itself) There's nothing worse than steaming down jump run (especially no wind/low wind) and watching the GPS tick down and the jumpers back on the tailgate having a tea party before exit.
So, in general terms the less wind aloft the less separation, never less than 5 seconds though. Separation should be a function of Groundspeed, bearing in mind again freefall drift is negligible below 20 kts.
If you have a mix of disciplines on board consider freefliers first, RW next and tandems always last, a large RW formation should maybe go first with a longer than normal separation for them. I usually let the load organisers sort this out and try and get an idea of what we've got enroute to altitude and make corrections accordingly.
So basically, tricks up the sleeve are plot your winds outwards from the dz starting with surface winds. Offsets for awkward wind conditions, disregard freefall drift below forecast 20 kts aloft, consider downwind exit points (not too far downwind!) for low surface wind conditions, arc method. Talk to the jumpers especially first out/last out and get an idea of opening points so you can "dial" in the jump run.
E-mail me if you want to talk more about it,
Regards
Leviathan