OK, lets give chornbro a break. 1st off, when people say "LR" they don't define it so it can be confusing. It may very well be that 2.0 Ω atties seldom (or never) cause issues with these devices (eGo class), whereas a 1.5 Ω atty will fry it if heavily vaped. It may also be that the eGo/Riva makes have made a design change, or that you just need to vape heavily enough in a short period of time to get it to overheat/stress.
I can tell you that many forum members who's information and opinions I take very seriously, have had these units fry fairly quickly using 1.5 ohm atties. Also, VENDORS have had returns and notices trends that LR atties have cause the MOSFET circuitry to be stressed.
So, try 2.5 Ω 1st. If that doesn't do it for ya, try 2.0 Ω. Lastly, I'd stay away from 1.5 but if you insist, go ahead. Just know as you reduce the ohms, history has shown, that you increase the risk of premature device failure.
Remember ohm's law: power = V*V/R where R is the atty ohm (resistance) value and V is the voltage (3.2 on many eGo models). Thus 1.5 ohms at 3.2 volts is 6.82667 watts. 2.0 ohms is 5.12 watts on the same device. That's a full 1.7 watts difference on devices that were originally designed for, say, 3.6 watts (IDK the actual design spec, but that's for a 2.8 ohm atty)
The above is for eGo type kits... the OP was talking about "skinny" 510's. See post #9 for the differences (and some of the other posts too). Most people can't stand the short battery life of a standard 510 batt and it's worse with LR's.