What is the rule for a series of third tones? I understand what to do if you have a series of 3 third tones, and the rules are well explained here. But what about 4 third tones in a row?


  这件大衣很特别，我也想买一件。


I'm guessing it would be wó yě xiáng mǎi 
Would that be correct?
It might be subtle, the series of tones would be 2-半三声-2-3. (半三声 means only the first half of the 3rd tone, without the rising tone part.)

Firstly 我也想买 could be separated as 我(也(想买)), and according to the rule about the 3rd tone sandhi, rule #4.1 (for 也(想买)) and #2 (for 我(...)) match and then leads to 2-半三声-2-3.