Tone 平仄 of the 5th character in a seven-character jueju 七絕 In writing regulated verses 近體詩, there's a saying "一三五不論，二四六分明。" (We don't care the tone 平仄 of the odd-numbered characters in each line, but we care about that of the even-numbered ones.)

However, Baidu's page about seven-character jueju 七絕 shows that the tone of the 5th character of each line is fixed.

I wonder if one has the freedom to choose the tone of the 5th character in a seven-character jueju.

Let's take a concrete example.  Is it ok to take a deflected 仄 tone at the 5th character at the first (out of four) verse?


  秋風拂澗泛桑葉，舉目棕巢掛禿枝。
  平平仄仄仄平仄，仄仄平平仄仄平。
  碧水浮鵝追舫艇，舟乘遠去土盧茲。[1]
  仄仄平平平仄仄，平平仄仄仄平平。
  
  [1]: 土盧茲 (Toulouse, capital of Occitane region in France)


Remarks:


In principle, I'm following Shiwen 詩韻 published by the Hong Kong Public Library (HKPL).  This is the standard for regulated verses in the HKPL's Chinese Poetry Writing Competition.  In practice, I'll first use my mother tongue cantonese to determine the tones 平仄, before verifying Pingshui Yun 平水韻 online.  Cantonese's accuracy rate is over 90% since it preserves 入聲 in medieval Chinese.  The rationale for sticking to an ancient phonetic standard for composing regulated verses nowadays is to maintain the universality of this genre of poems: if poets compose in their own dialect, the 平仄 tones won't be carried to other dialects.  This inhibits others from appreciating the poem, and this genre would loss its influence in the long run.
I know very well that the first verse has a problem of "isolated plane tone" 孤平 according to "the second school of thought" 乙派 in the linked Baidu 百度 page, but let's adopt the "first school of thought"'s 甲派 viewpoint on this issue.
From my user profile, I'm neither a writer nor a poet.  I've written some regulated verses simply to cultivate my character 陶冶性情.
It is actually a big topic on the tone of Chinese poetry, even in different dynasties the rule is slightly different. I recommand you read Wang Li's (王力) book named 《诗词格律》, which has a systematic description on it.