Radicals : How to remember suffix-es, readings and positions?


There are 214 radicals, and their positions can be either Hen, Tsukuri, Ashi/
Ashi Variant, Kanmuri, Nyō, Tare or Kamae/ Kamae Variant.  
One example 衝(oposition), so this kanji is made of the kanji 行(to go) and
重(weight), 行 stands for gyo-gamae(kamae position) and this is where I need
help:  
  
-) Is it true that the 行 makes the semantic part and 重 the phonetic part of the kanji 衝?   
-) If yes is it always so that that the kanji which presents the radical of the main kanji makes the semantic part and the other kanji the phonetic part?   
-) Some radicals have suffixes based on their position like ninnyō, wakanmuri, tsutsumigamae, etc., but what with the others with suffixes like **gashira** does it mean that they are phonetic and semantic(phono-semantic) kanjis and they can be placed **anywhere** and does that apply to the **other kanjis which don't have those suffix endings** like : ~hen, ~ben, ~ri, ~kuri, ~tsukuri, ~ashi, ~kanmuri, ~ganmuri, ~nyō, ~tare, ~dare, ~kamae, ~gamae and the ones with this suffixes are they always semantic or can they be phonetic or even phono-semantic?




It's true that 衝 is traditionally / generally considered as [ semantic 行 +
phonetic 重 ].

However it is not always the case. For example [衡]{こう} ( as in 平衡, 均衡 ), which
looks pretty much like 衝 in appearance, is believed to be from semantic [ 角 +
大 ] ( said to represent "a yoked ox" ) + phonetic 行.

Similar cases can happen also with other radicals. For example, you can
compare:

> 闇 / 閣 / 閲 [ semantic 門 + phonetic 音/各/兌 ]  
>  問 / 聞 / 悶 [ semantic 口/耳/心 + phonetic 門 ]  
>  開 / 閉 / 間 / 関 [ semantic + semantic ]




It's true that 衝 is traditionally / generally considered as [ semantic 行 +
phonetic 重 ].

However it is not always the case. For example [衡]{こう} ( as in 平衡, 均衡 ), which
looks pretty much like 衝 in appearance, is believed to be from semantic [ 角 +
大 ] ( said to represent "a yoked ox" ) + phonetic 行.

Similar cases can happen also with other radicals. For example, you can
compare:

> 闇 / 閣 / 閲 [ semantic 門 + phonetic 音/各/兌 ]  
>  問 / 聞 / 悶 [ semantic 口/耳/心 + phonetic 門 ]  
>  開 / 閉 / 間 / 関 [ semantic + semantic ]

