It is correct that the JTAG pin description is not available yet. I have discussed that issue internally and we came to the conclusion that we will make it available for the public within the next few days.
If you use your custom JTAG adapter you are completely on your own. No warranty, no support, you have been warned. As we do not have this adapter here I also cannot tell you if it works to program the HLP.
In case it works, please let us know, so that other customers have this information as well.