I have been using my Form2 for a couple years mostly using standard resins. A customer came to me wanting something printed in a PP clone so I purchased the Durable resin. When I print the parts and cure them in my home built heat and UV unit at the proscribed setting, the parts still feel too soft and flexible and are not a realistic clone of PP so the parts will not function and work properly in the customer’s application. When I talked to Formlabs support they recommend that I use the FormCure for the best possible results, bit they will not do a test print of my specific part nor will they offer a money back guarantee if the FormCure will not give the desired results. I am looking for someone that has Durable resin along with a FormWash (which I do have) and a FormCure that is williung (for a price of course) to print, wash, and cure my parts so I can see if the expense of the FormCure will give any better results than my home built cure system.
You should give your location if you want better chances of finding some help 
Formlabs unfortunately is very reluctant to printing custom samples but they do offer standard samples for free, I think you’ll find the Durable sample resembles PP quite well.
Durable does indeed require propper post-curing, as seen in this page the tensile modulus (stifness) increases by a whopping 130% after 60min at 60° and the recommended UV exposure.
Also- how well it analogs PP is directly affected by exposure to oxygen in post cure.
If you can- cure under distilled water in a container that does NOT filter out UV light…
Or- I get even better results with Wicked Engineering’s CureGel.
be aware- it will approximate PP in its feel and resistance to abrasion. It flexes very much like PP, but it will NOT have the elastic memory of PP. sadly- no uv cured resin has much in the way of solid memory performance because the polymer chains simply are not as long and contiguous as in a hot melt injected material.
Its a close visual and tactile approximation, and a less close physical approximation… But its as close as you are gonna get in any printed material I have seen.
The question is what the customer’s application actually requires.
I oscillate between using Durable and Tough depending on exactly which parameter is going to be more important to function.
Can I ask where you find the material lacking?
One of my issues with Durable is that it has no memory. If you have a part that is thin or subject to some force, it is going to permanently deflect. That’s not going to change with a better cure.
I get a better cure when I have used Curegel from Wicked Engineering. They also sell a Curebox. They might be willing to make a test print for you - they have been very helpful to me.
I suspect you just might be running into the limitations of the material, but hard to tell without more information about what you find lacking in your part.
I don’t know if the form cure will give you the “expected” results, but what I can say is that it really helps with proper post-curing. The nail spa we customized with 405nm LEDs always left the parts undercured, even if left in for ridiculous amounts of time (most probably the proper temperature for curing was missing). Durable will indeed become noticeably stiffer with proper curing, but as I said, I can’t tell you if it will give you what you expect - neither can Formlabs or anyone else, unless you quantify your expectations (e.g. tensile modulus +x%).
As @JohnHue said, if you post your location, it will be easier for someone to tell you if they can make a test part for you.