Mesa Precision altitude will save 8-10oz over the factory stock.
Mine wasn't quite that drastic. The short action Ridgeline stock was right at 32 oz with a front rail, the Mesa came in at 30 oz.
I've used a few Mcmillans with a R700 inlet and a Sendero channel on LA Christensens. The LA Edge filled McMillans run about 27-28 oz. They have all been simple to set up and use with minimal fitting. The Mcmillan Sendero barrel channels are really close to fitting right out of the box and require light sanding for proper fit. The stocks do require additional clearance below the bolt release, but a small flat file works to clear it quickly.
The bottom metal and mag box is different on the Christensens and they don't fit quite like the Remington parts. You'll have to shave material from the bottom of the mag box to keep it from binding between the bottom metal and receiver and you'll most likely have to trim a couple threads off the front action screw. The Christensen bottom metal doesn't fit flush with the stock, so if flush is important to you, you'll need shim washers or bedding to get the fit correct, or you can just use Remington parts to avoid the fuss.
Overall, the mods take just a few minutes and the stock upgrade is absolutely worth it. My LA Ridgelines are ~ 8.5lbs with 28 oz optics mounted (Nightforce NX8 and Vortex AMG)
The Mesa took quite a bit more inletting to get right. The barrel channel wasn't straight and the bottom metal didn't fit at all. After additional inletting, I ended up bedding the bottom metal to get the final fit correct and the barrel channel ended up with excess spacing around the barrel. It works, but I wouldn't do the Mesa again for a Christensen. Actually, I'm not sure my Mesa would have worked well with a straight Remington 700 it was designed for.