The essence of a suhhah is its shade. If there is more sun than shadow, it is invalid. 

'In His shadow, I delighted there and there I sat, and the fruit of His Torah was sweet to my palate.' (2:3) בְּצִלּוֹ֙ חִמַּ֣דְתִּי וְיָשַׁ֔בְתִּי וּפִרְי֖וֹ מָת֥וֹק לְחִכִּֽי 

אֲוַז הַבָּר הַמְּשׁוֹטֶטֶתבַּמִּדְבָּר. כְּשֶׁרוֹאֵה אֶת יִשְׂרָאֵל עוֹסְקִיםבַּתּוֹרָה אוֹמֶרֶת. קוֹל קוֹרֵא בַּמִּדְבָּר,
פָּנוּ דֶּרֶךְ יי, יַשְׁרוּ בַּעֲרָבָה מְסִלָּהלֶאֱלֹהֵינוּ, וְעַל מְצִיאוּת מְזוֹנוֹתֶיהָ בַּמִּדְבָּראוֹמֶרֶת. אָרוּר הַגֶּבֶר אַשֵּׁר יִבְטַח בָּאָדָם,
בָּרוּךְ הַגֶּבֶר אֲשֶׁר יִבְטַח בְּיי וְהָיָהיי מִבְטָחוֹ: 

The Wild Goose flying in the wilderness, when it sees Yisra’el busy with Torah, is saying “A voice cries, Prepare in the wilderness the way of YHVH, make straight in the desert a path for our elo’ah. And upon finding its food in the wilderness, it says, “Cursed is the man who trusts in human beings…” Blessed is the man who trusts in YHVH, and YHVH shall be his assurance.”