Looking at this Tshuveh (Siman 'ט) with an iota of objectivity you might say that he was using RAYH"K to make his point, and not so much because he held of him as a m'kor. Sort of like what the Satmarers do when they wanna make a point regarding their favorite subject, Zionism. They'll bring Belzer letters and show it to a Belzer, and then they'll show letters from the Rebbe Rashab to a Lubavitcher, and so on. But then again, we all know that when asked why he's taking Rav Weisz as dayan in the Edah when he's not a kano'i, the Satmar Rov said that a Talmid Chochom can become a kano'i, a kano'i won't become a talmid chochom so quickly... Which is what happened; Rav Weisz fell in line with the Edah theology very nicely, just like the SR foretold. We bring you the Tshuveh in Minchas Yitzchok, and then the Tshuveh in Kol Yisroel from Rav Kook in 1933.
קול ישראל courtesy of תוך כדי דיבור on Otzar haChochmah. Minchas Yitzchok courtesy of HebrewBooks.