Quick question on searching Sales Orders

I have this script working, but the search results are returning cash sales, invoices and sales orders. I suspect that I have the filter for sales orders set incorrectly. Customers always have only one sales order in this case so i have set the loop for only 1 until I can figure out how to filter it correctly.

I have searched the reference guide and I am not sure what the filter should be.

Anyone know or at least know where else I can look?

Here is the code:

 function beforeSubmit(type)  {    if (type == 'create')    {    var cashsale = nlapiGetNewRecord();    var custId = cashsale.getFieldValue('entity');    var columns = new Array();    columns[0] = new nlobjSearchColumn('internalid');    columns[1] = new nlobjSearchColumn('custbodysovin');    var filters = new Array();    filters[0] = new nlobjSearchFilter('name',null,'equalTo',custId);    filters[1] = new nlobjSearchFilter('type',null,'equalTo','salesorder');    filters[1] = new nlobjSearchFilter('mainline',null,'equalTo','T');    var salesorders = nlapiSearchRecord('transaction',null, filters, columns);      for ( var i = 0; salesorders != null && i < Math.min( 1, salesorders.length ); i++)     {     var salesorder = salesorders[i];       var sovin = salesorder.getValue('custbodysovin');      cashsale.setFieldValue('custbodycsvin', sovin);     }    }  }