There is a reason you have medium and low on flashlights… 
The LED wont sweat much before you find the light too warm to hold anyway as long as its copper mounted.
I think many people exaggerate the heat “issues” with the P60 format.
Until someone shows me some numbers comparing a P60 that has a copper mounted LED (and a copper ring between the pill and the body), compared to a similar sized light running 3 amps showing that the P60 are highly inferior in terms of lumen sag, im not buying it.
Running 3 amps in a P60, or P60 sized light is only a matter of how you use the light, and the environment you use it. With copper mounted LED, and maybe even a little copper ring between the P60 and the body, the main issue is in my opinion the surface area.
Put the light in a backpack, on high for 30 min in a closed, tight, environment and the body will reach 80+ degree. I would worry about the battery before I would worry about the LED, but that is me.
Use a 3amp P60 in the winter (around freezing point), some wind and it barely works as a good hand warmer when used for longer periods.
Running 2,8A in a Convoy S-series light on aluminium mcpcb, that I would question more, there is just not enough surface area to get rid of the heat and the mcpcb is a bottleneck that will let the LED run at higher temperature. The main problem with running 3A in a P60 for some time is the light is just not that large (not enough surface area to get rid of the heat), but who said you have to be able to have it tail standing for 10+ minutes indoor without the light very hot? There is a reason why you have medium, you dont need to use high ALL the time…
Im running 2,6A-3A on high in lights that are slighty smaller than P60. Usually 3A in P60 (sized), and often 3+ if its larger. Yet, I use high probably 90% of the time I use my lights… My point is, its mostly a matter of how you use your lights, and the environment you use it in. To some, 3A is perfect, to others its too much. I would not treat a copper mounted XP-G2 any less hard than a copper mounted XM-L2 as long as we are talking about a compact single cell light. Its not like you are going do damage the LED as long as its properly mounted.
A comparison between a Convoy M2 running 3A, and aluminium mcpcb vs a P60 with copper mounted LED, and a copper ring between the pill and body would be interesting to see.
People rarely say 2,8A is too much in Convoy M2, (or M1) with alu mcpcb, but 3A in a P60 with copper mounted led, then you are way over your head…
Even in small modified Maglites, shortie AA Maglite and other small lights, close to 3 amps seem to be fully accepted as long as there is a copper pill, but 3A in a larger P60 despite running copper mcpcb, then you are over your head according to the same people it often seems.
I use 3A high and copper mcpcb as default options for lights in that size. For me, and the way I use my lights, that is no issue.
To OP, if you are going to mod it, why not start with a 3A Qlite, and if you think its too much heat on high, and you want less light, just remove a 7135 or 2…