I've recently combined Dragon and RFM parts to get a more accurate mantlet for my recent Tiger project.
As you can see in the picture, the inner part from Dragon (grey) fit the RMF mantlet (yellow) well with just a bit of sanding along its edges, as it is ever so slightly too large out of the box.
The gun tube collar seen in the picture, also from Dragon, fit the RFM part without modification.
Now, before David B is having fits from me claiming to need an RFM mantlet to be more accurate, see the below image. The RFM mantlet is not 100% correct, but closer than the Dragon part. Now, Dragon provide a mantlet more or less identical to the RFM part in some of their recent Tiger kits, but I haven't made sure that I will not need them for those projects. The RFM mantlet is a spare in most of the RFM Tiger kits (of which I've got every one, but have yet to build one), so it is a safe "steal" from there.
I've also used Feifels and mantlet from RFM to upgrade a projects based on a Tamiya Tiger kit (which also partially received a Dragon set of road wheels).