Changing EXTJS AJAX method from GET to POST will cause any performance problems

Changing EXTJS AJAX method from GET to POST will cause any performance
problems

I have an extjs request like this:
Ext.Ajax.request({
url: someUrl,
method: "GET",
params: paramArray,
success: function(response){
var responseText = response.responseText;
//DO STUFF
},
failure: function(response ) {
// DO STUFF
}
}); // end of ajax call
Now because the method is "GET", the number pf params in the url is
limited. What is the best way around this? If i just change it to "POST",
will it cause any side effects? (poor performance etc). The method should
logically be a "GET" because it is not an update, just a fetch but to
solve my ucrrent problem with parameters, I want to change to "POST".
Unless of curse there is a standard solution to this problem.