I guess it depends on some information that we don't have.
The "main cables" (which hopefully for your safety aren't mains cables), may be significantly thicker than the other smaller cables and have a negligible resistance.
If you want to model the resistance exactly, go ahead and measure the main cables as well, and add it in series with the parallel mess of wires. Unless you are doing something unsafe, the resistance of these wires really shouldn't make a difference.
On the topic of safety: If you are doing something where you are drawing enough current that your putting 50 wires in parallel to solve the problem, that isn't the solution your looking for. While it will lead to a lower overall resistance, there will still be fairly high current going through each of the wires, and you don't want them to burn up. Any power dissipated by your makeshift resistors will turn into heat, and potentially a lot of it.
Please make safe decisions, especially if you aren't that experienced with electronics yet, and avoid high voltage until you know what your doing.
And if you insist on still going through with this stuff: please keep one hand behind your back at all times. High voltage can really kill you if you aren't careful.