I wouldnt bother to include the 9465 with the 1040, it just takes too long for the client to hear back this way.  Just have them make as large of a payment as they can at the time of filing, then have them make any payments they can afford to using IRS Direct Pay until they get their first bill.

Once they get the first bill, then they know the balance has posted to their account, then they can go online and create an IRS account (or they can call) and set up their own payment plan, its much quicker and keeps you out of the payment portion of the whole thing and they wont be calling you wondering when  the payments will start coming out.