My $0.02
My first Mesa was a 2001 Triple Rectifier. I started with a few Boss pedals in the loop for a couple of years but was never happy with how they performed. I blamed the pedals and tried other brands, even bought a TC G-Major, which was an improvement, but the amp always sounded ‘weaker’ with the FX loop switched in. I tried using the EQ in the G-Major to tweak things but it always just made matters worse (which I now know is because of using an EQ in a parallel FX loop). I was also not happy that the noise gate in the G-Major was useless in a parallel loop, and any pitch & modulation effects always sounded weird. I found myself constantly fiddling with knobs and settings.
That all changed in 2007 when I bought my Roadster. Same G-Major, but now in a series FX Loop. I still use that same G-Major today with the Roadster and TC-100.
The owners manual is always a good resource. Start with the FX send at about 11:00 and keep your channel master settings conservative. I never went above 10:00 in channel 3 Modern.
In the end I think you would be much happier with a series FX Loop. With the money I spent trying different pedals I could have just had the amp modded. Even a ‘high end’ unit like the G-Major couldn’t fix the cons of a parallel FX loop for the average musician.
Dom