I did the inline thermo mod last year and like the smaller temp delta, using a 180 thermostat. Problem is, with the cooler air of winter, I was getting running temps in the 160's and 170's, too cool for operating and not hot enough for cabin air. So I've switched out the thermostats to a 195. The temp delta is still fairly small, albeit at higher temps and I can do cabin heat that's actually nice and warm. No change in mpg or performance noticed. Plan to switch back to 180 for summertime. Both stats are Stant, with hole drilled.

 

I think the thermostat brand makes a difference.

I'm running a Summit 180 stat and my temps are 177-183.

My only problem with this mod is the intial temp drop when the thermostat first opens. Might have to drill the sensing holes.

 

I get warm air after temp reaches 140's, and when it passes 165* heater temp is close to its max & not much diff when in 180*, you may want to check your heater core for flow to see if it's not partially clogged, that can lead to poor heat,
,,, and curious what is your operating temp with 195* T-stat that leads to having better heat in cabin, your rover seems to be running very nice & cool that can use a 195* Stat & keep cool temps,

 

thanks for the heads-up on matrix flow. Operating temps with the 195 range from 183-197. With occasional, momentary dips to 177 and same up to 201. With the 180, it was 168-177, with the occasional dip to 163 and up to 190 (max range observed ). Was blowing nice and warm, but with the warm air came the lower operating temps, generally. Now it's nice and hot air, with around 190ish operating temps. Not a huge difference, was interested in the warmer air and to see if higher operating temps would give better mpg. No such luck on mpg.