Hi @manal,
I am sorry about the late answer.
In HB+ you cannot use proxy geometry – to my knowledge. I don’t know if @sarith remember any hidden implementation in HB+.
The 5-phase method in HB+ is using the Klems BSDF for both the 3-phase and 5-phase calculation. The recipe is not set up to use a tensor tree BSDF for the direct sun light calculation in the last part of the 5-phase recipe.
It is probably not the answer you want to hear, but for what you are trying to achieve, it is easier to run it outside Grasshopper using your own command line scripts. When I did my master’s thesis back in 2019 I also learnt this as I was trying to use tensor tree BSDFs. I had to learn how to use Radiance using command line so I could run it exactly as needed – I used Sarith’s tutorial that he linked to in the other topic, also mentioned under Advanced Tutorials here.