Add item Group to order via SuiteScript

Does anybody have a working code example of how to create sales orders that contain an Item Group via SuiteScript?

I have been banging my head against a wall for about 24 hours here... Netsuite throws an INVALID_NUMBER error with these (gloriously non-specific) details: You entered "{rate}" into a field where a numeric value was expected. Please go back and change this value to a number.

Here's what I'm doing: var newSalesOrder=nlapiCreateRecord('salesorder',{entity: 3751090, recordmode: 'dynamic'});
newSalesOrder.selectNewLineItem('item');
newSalesOrder.setCurrentLineItemValue('item','item',114270); // ID is for a itemgroup
newSalesOrder.setCurrentLineItemValue('item','quantity',1);
newSalesOrder.commitLineItem('item');
nlapiSubmitRecord(newSalesOrder,true,false);