Migration options Forms 4.x with 2.5 triggers

Hi,

At present we're rolling out a new system but need to retain a legacy sub-system (possibly for 2.5 years from now). Just wondering does anyone have experience with the configuration below or suggestions with the migration of such a system?  

                       TIA,
 
                                    Michael.
 
 
	    Oracle database 8.1.7.4.1
            Oracle forms 4.x (some have v2.5 triggers)
            Platform: VMS