Help needed with some conditionals (forum/first post)

[Triky]

I need to show a customized postibit_lagacy template in some forums. And this should apply only to the first post of the threads.

So, I founded these conditionals:

<if condition="in_array($thread['forumid'], array(1,2,3,6))"></if>

... and:

<if condition="!$GLOBALS['FIRSTPOSTID']"></if>

My question is: how should I use them in the best way?

Should I do something like this?

<if condition="!$GLOBALS['FIRSTPOSTID']" AND in_array($thread['forumid'], array(1,2,3,6))">

My custom postbit_legacy code.

<else />

Original postbit_legacy code.

</if>

Is this correct?