Q. It says that succa is one of the few mitzvos that people do with their complete body. Since sitting or sleeping under a table that is ten tefachim high is not considered like being in the succa, should one try to sit by a table that is less than a meter high (approximately ten tefochim) so his feet will also be in the succa?

A. Kemotzeh Shallal Rav (Sukos p. 9), quotes in the name of Horav Shlomo Zalman Auerbach zt’l that there is no question that one would comply lechatchila the mitzva of suka, even if his feet were totally outside the suka, as long as the majority of him is inside. However, the HaGra’s recommendation of being totally inside, in a manner similar to Yishuv Eretz Yisrael or immersing in a mikva, would be missing. See also Shalmei Toda (Sukos p. 101), who amply discusses the above.
Horav Shlomo Miller Shlit’a that there is no valid source for avoiding seating next to such a table. He also pointed out that the vast majority of tables are well below the ten tefachim height. (The average being 72cm. to 74 cm.).

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a