How do you mean strict? I warn to not install in the %ProgramFiles% because of the known problems that the restrictive permissions on Vista or Win7 of this system folder causes with these legacy games, but I don't prevent the user from installing there, if they wish. It is true that the first versions of the patches didn't allow the user to use anything other than the default VU install directory (I was just learning to use NSIS, then), but that has not been the case for the past few years. I have become much more proficient at NSIS scripting since. The only thing that I don't give an option for is the location of DOSBox, but this is so the shortcuts don't get broken when the user upgrades to a new version of DOSBox and I don't have to redo all of my patches and installers whenever a new version comes out.
If the patch you are using does not allow you options for installing, you have very outdated version of the patches. Always get them from my site to be sure that you have the latest.