[TowerTalk] Dipole Centre - Proximity To Metal Mast

[Jim Martin - MM0BQI]

I have a small garden and just manage to squeeze a 40/80 loaded dipole from the roof to the fence.  The centre of the dipole is currently unsupported six feet above the flat roof and I would like to increase this to about fifteen feet by supporting the centre with a fifteen foot metal mast.  Can I secure the dipole centre directly to the metal mast (2 inch diam pole) or should I use some form of insulated stand off?  The dipole ends are only a foot from the metal end supports, will this be having a detrimental effect on performance?
With this sort of compromise you need to squeeze every bit of advantage where you can so your comments and advice on what is actually worthwhile doing would be appreciated.
Thanks
Jim,  MM0BQI