bracha on sleeping in sukkah - Rogatchover

Will get to part II of previous post bl"n soon, but I almost forgot apropos of the discussion about sleeping in the sukkah - the Rogatchover has an interesting sevara to explain why no bracha. He suggests two dinim in sukkah: 1) a mitzvah kiyumis of being in sukkah 2) an issur aseh of being outside the sukkah when one should be in. When it comes to eating, a bracha is recited because there is a positive chiyuv, a mitzvah kiyumis, when having a meal to do so in sukkah. However, when it comes to sleeping, there is simply an issur aseh of not sleeping outside sukkah. Of course one needs proof for such a sevara, but for that you will have to do your own homework because I don't have enough time. This Rogatchover is found in Mefa'aneyach Tzefunos, p.164 (just an aside: a recall a similar sevara of sukkah being an issur aseh being in the Minchas Chinuch, and discussed as well in Esvan d'Oraysa.)