Hi,
I have been struggling with high SHBG also … my story is at High T, FSH, SHBG, Low E2 No Libido. My Lab Results (pellets) - #12 by traveling-man
The doctors have not been able to determine the cause of the high SHBG. Like you, I take boron, and have tried stinging nettle root. For a while, I believed the boron was working, but now do not think so now as my SHBG has continued to rise. I’ll stop taking boron when I run out. 
I hope you will keep your thread updated with what you find. I’ll be watching!
Thanks.