Fitting 問題.....能用短一點的龍頭去遷就上管嗎?

大家好, 我是香港的車友, 有些問題想請教一下
我個子不高163cm, 去了competitivecyclist.com 後, 建議水平上管要50公分, 但香港市面水平上管要50公分的車架不多(在台灣多幸福), 請問能用短一點的龍頭去遷就上管嗎? 會影響到姿勢和效率嗎?

(補上fitting 資料)
Measurements
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Inseam: 71.8
Trunk: 56.3
Forearm: 32.7
Arm: 61.1
Thigh: 55.5
Lower Leg: 46.6
Sternal Notch: 132.3
Total Body Height: 163


The Competitive Fit (cm)
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Seat tube range c-c: 46.5 - 47.0
Seat tube range c-t: 47.9 - 48.4
Top tube length: 50.6 - 51.0
Stem Length: 10.2 - 10.8
BB-Saddle Position: 61.2 - 63.2
Saddle-Handlebar: 47.6 - 48.2
Saddle Setback: 3.4 - 3.8


The Eddy Fit (cm)
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Seat tube range c-c: 47.7 - 48.2
Seat tube range c-t: 49.1 - 49.6
Top tube length: 50.6 - 51.0
Stem Length: 9.1 - 9.7
BB-Saddle Position: 60.4 - 62.4
Saddle-Handlebar: 48.4 - 49.0
Saddle Setback: 4.6 - 5.0


The French Fit (cm)
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Seat tube range c-c: 49.4 - 49.9
Seat tube range c-t: 50.8 - 51.3
Top tube length: 51.8 - 52.2
Stem Length: 9.3 - 9.9
BB-Saddle Position: 58.7 - 60.7
Saddle-Handlebar: 50.1 - 50.7
Saddle Setback: 4.1 - 4.5