I am not really the one to ask because once I started getting a regular meditation practice my crown chakra exploded and since then I have been struggling with getting grounded enough to practice. Qigong is good for grounding but my case was so difficult that even the advice that works for most people like standing meditation proved ultimately to also case problems so Know I just do six healing sounds (qigong), intfulow, pilates, wegiht training and some physical grounding excercises. THat works but takes forever.

What I think is that most types of qigong will provide balance and an initial help gaining jhana and maybe slightly with vipassana as well but that only certain types of qigong realy spead up the insight process. I think most qigong will help open channels, balance chakras and organs and make you emotionally and physically very healthy and balanced but only certain types of spiritual qigong will help Vipassana. Primordial Qigong and Jenny Lambs Yi Gong are two such systems I think speeds up Vipassana Because they are seen in Taoism as in themselves sufficient for enlightenment if practiced enough and they work really deep on the alchemical process as laid out by Taoism and found in highly similar versions in other traditions. Wether it is actually quicker to add such a system to Vipassana or it is better to spend all the time just doing Vipassana I really don`t know but I am pretty convinced they at least work well on the same thing. For me That ultimately does not matter as I want balance and I want to smooth out the insight cycles etc. and I am willing to slow down to achieve that. But I don`t think adding a well chosen spiritual qigong will slow things down.

As to BK Frantzis, everyone says his stuff is good, very safe, what is in his books can generally be learnt from the books, it is a genuine Taoist lineage (hard to come by) but it is slow and it is not a system that generates high energy levels quickly like say Kunlun will do. From what people say it seems to me that you won`t go wrong doing only that but I have yet to see anyone claim stream entry from it although I am sure it happens. For enlightenment I am convinced Vipassana with noting is much faster although they are very similar and can be perhaps combined and some say his method eventually evolves or should evolve into Vipassana. But I also think his method is much more balanced, safe, healthy and in general a comfortable ride tahn doing only Vipassana. What I think is an effective and balanced approach is to do Vipassana combined with a more high energy qigong that is also known to be balancing. Jenny Lambs Yi Gong has the reputation of both being very powerful and balancing so thats a good combo. Not everyone likes KAP but many do and get a lot of success and have a very balanced safe ride and avoid most common problems such as disconect from daily life, loss of sex drive, becoming too soft etc. in addition it really helps depth of meditation and I belive integrates kundlaini really well and helps do the alchemical process. Sprngforestqigong has gotten very, very good feedback but there is a lot of uncertainty wether it helps the alchemy much as it is built mainly for health and healing. There are a bunch of other choices as well. Stillnes movement for example seems very good but maybe a bit hopeless to COmbine with Vipassana and might need to be practiced on its own or might not be so usefull to combine with vipassana as I think it sort of has an insight component built in. Quality of teacher is also a factor. Kunlun is a modified version of Yi gong but the teacher Max is known to be a liar and seems like a narcissist to me whereas Jenny Lamb seems balanced and nice and everyone that has taken KAP has good things to say a bout the teachers as people although they might not have thought the course was good.