After making some experiences with TIR Lenses on a black Convoy S2+ with XML2 U2-1A, I decided to make the same experiences with the XPL-HI U6-3A from the Convoy S2+ Desert Tan version.
Here are my conclusions, before showing the results:
- the pebbled (hive) lens, the frosted lens and 2 other lenses (narrow beam) produce good beams and/or spill.
- using the plastic holder helps in 1 lens (narrow), is neutral in 2 lenses (pebbled and frosted) and does not fit on the others.
- the white gasket for the LED could only be used in 1 situation, what is bad as it allows to centre the LED and the holder/lens.
- using the plastic holder requires some careful, as the hot temperature of the wires may provoke it to melt and to damage the plate, led or lens. So, using the plastic holder in contact with the wires is a risk that must be taken into account.
Let’s see!
THE LENSES and HOLDERS:
6 lenses were tested, 1 lens holder was used

1st LENS
This lens was originally from a Stainless Steel flashlight, used originally with a small LED (don’t remember the type).
It produces as narrow and intense hotspot (despite it can’t be seen clearly on the photos) as it has a frosted centre, and has one of the narrowest spills of all lenses. It was the only TIR lens used with the XPL-HI original gasket. The plastic holder was not used, as it was not used the glass lens nor the o-ring.
This is one of the nice lenses to use with this type LED in terms if fitting the led and the head.

2nd LENS
This is the closest type of lens that one can get from Simon’s store. I bought mine somewhere else, but these are the most appropriate lenses for this flashlight in terms of diameter, even if the plastic holder had to be slightly modified.
This lens produces a better beam with the holder than without it. I used two configurations, that are shown below.
PART A)
TIR + Glass lens + O-ring. No gasket, not plastic holder.

PART B)
TIR Lens + plastic holder. No glass lens, no gasket, no o-ring.
The beam is more defined and centred, has a better look in terms of output.

3rd LENS
This is one of the worst lenses used. I can’t remember but maybe this lens is not originally made to use with XML2 or XPL-HI LEDs. In the centre it produces the effect of magnifying lens, what produces a hideous beam that can be seen below.
This TIR was used with glass lens and o-ring. No gasket and no plastic holder, as none fitted the light with this lens.

4th LENS
Another bad beam, from a slightly different TIR, that also has the “magnifying” effect in the middle. This effect is not so big as the previous, but it produces a squarish effect (barely seen in the photos, sorry) and some kind of concentric circles, as the Lens #3.
This TIR was used with glass lens and o-ring. No gasket and no plastic holder, as none fitted the light with this lens.

5th LENS - FROSTED
This is another good TIR to use with the XPL-HI, as it doesn’t give problems with the hotspot. This lens produces a floody beam, but a small soft hotspot can be detected in the middle; nor very pronounced, though.
The spill is not wide as an XML2 LED, but it is enough to illuminate a room in all directions.
I used it in two configurations. There is no significant difference between using the holder or not, in terms of beam.
PART A)
TIR Lens + plastic holder. No glass lens, no gasket, no o-ring.

PART B)
TIR + Glass lens + O-ring. No gasket, not plastic holder.

6th LENS
PEBBLED/ “Hive”
This TIR lens has a 60º angle. With the XPL-HI it produces a floody and homogeneous beam, apparently with smaller spill than with a XML2 LED. However, I can’t measure this accurately.
There are no significant differences in terms of beam using or not the plastic holder.
PART A)
TIR Lens + plastic holder. No glass lens, no gasket, no o-ring.

PART B)
TIR + Glass lens + O-ring. No gasket, not plastic holder.

And this is it.
Conclusion: XPL-HI can be used with TIR lenses, depending on their type. Attention must be given to the contact with the holder and the wires. Pebbled and frosted lens work well for floody beams; for narrow beams, appropriate lenses must be used (similar to XML2, not those for other types of LEDs, I guess).
Hope this helps 
Best regards!!!