1. Why are you even creating a <form> element? Why not simply use Ext.Ajax.request?
2. You can't use renderTo or applyTo inside a layout. You could use 'el' instead, but I wouldn't recommend this method.
ad 1) changed successfully to Ext.Ajax.request. Now it works. Thx.. (this approach certainly makes more sense..)
ad 2) but applyTo works in my case. What are the flaws/restrictions/problems if I continue to use it. What other alternatives are there (besides el, that you don't recommend)?
When you use 'applyTo' it will first render the panel to the 'request-panel' and then move it to the layout.
Using 'el' it will first move the 'request-panel' element to the layout and then render the panel.
Both methods will work, but on slow browsers the second one looks better.
What does 'request-panel' contain? If it only contains Ext components then you shouldn't be using renderTo/applyTo/el at all, but use items instead.