Once they get used to landing some where else it is very though.
Especially, if that location is significantly higher then the loft.
I doubt you can change that at this point.
What I would say, when you start young birds next time follow my instructinons from the other posting relating to training very carefully.
Especially the landing infront of the loft part.
I realize some loft locations are though but I have seen this breed trained to fly above 15 story buildings and then dive in between these buildings and make multiple turns around different apartment buildings to get to their loft on the ground with out landing any where.
I have seen a gentleman get his birds out of the ground floor loft, then walk them with a stick around the block like a sheep herd and then fly one at a time, when he is done walk them back to the loft.
Though, but very much doable.
If not sitting on the roof tops they are sitting apples for hawks.
As far as the time to fly it is very difficult for me to say anything not knowing your surroundings.
Heavy hawk areas, people tend to fly them very late in the afternoon.
I think, the hope here is that the hawk had enough time during the day to catch something and won't bother the birds.
If this doesn't work very early in the morning could be agood shot.
In the past, when I lived in San Mateo, I flow my birds at noon.
It doesn't get hot there much and with the heat of the noon sun the birds had a tendency to get very high very quickly.
This helped the young birds in training but once they start charging the coop then they were in the range of the coopers.
The best approach in my opinion, at least for our area, is to really understand the migration patterns of the predatry birds.
For example, once it is October 15th I will not fly a single bird here until it is past April 15th.