[TowerTalk] Vertical on Roof

[Edward]

I will be installing a Steppir BigIR on the roof, approx 25' high. The antenna would sit 6' above a large air conditioning unit. 

I plan to run some resonant radials. Problem with this is that they need to be run 6' below the antenna before I can spread them out flat and fish them underneath the HVAC. Not feasible to run them at a slope. 

I was also going to tap into the HVAC unit for additional ground plane as that's a large hunk of metal. 

Is the above the best approach??

Thanks,
Ed 7Z1ES