[TowerTalk] Dacron rope as an insulator

[Jim Thomson]

How good is dacron rope, as an insulator for HV?      I am planning on using  .3125 dacron rope as an overhead truss for the shortened  80m rotary dipole.
One length going out each side of the mast.   They will terminate on the mast, aprx 4 ft above the 80m dipole, with a small turnbuckle on each side of the mast. 
The other ends will  terminate 15 ft out each side of the main trunk section, which is 2 inch OD tubing.   This will also be just a few inches  inboard of the T bar
capacity hats.  Balance of loading is  done with the tornado drive, which consists of a pair of compressible 6-12 uh coils at the feedpoint. 
Going  out 15 ft  will be at a HV point, esp  since thats also way outboard of the 6-12 uh coils  at the feedpoint. 

Will 15 ft be enough to stand off the peak V....esp when soaking wet ?    IF each side is opposite polarity, then it gets even worse, as the potential  difference
right at the mast could be substantial under some conditions.   Or do I need to install an insulator  on either side of the mast, right at each turnbuckle ? 
Id rather not have to install insulators if not required, but have no experience with dacron + HV. 

Jim  VE7RF