I have managed it outside ePO using DLPAgentInstaller.x86.exe /quiet /norestart
I haven't tried those switches in the install option in ePO you may want to.
We also made a custom package with those command line options that worked OK for us
I have found that the number of knackered DLP upgrades after not enforceing the reboot was too high for us so now we just live with it do it out of hours and warn users in advance.
Will give it a go. Did you deploy using SCCM or such or point users to a share?
We actually deployed sometimes using ePO and the EEDK kit to create custom packages, you can also just use psexec or similar to create a remote command prompt against a PC and run from there.