Pitching champagne yeast to improve attenuation (wee heavy)

I have a wee heavy in primary that started at 1.095 and, after a week, has attenuated down to 1.038. I'd like to get it down another 14 to 16 points (1.022-24) and am considering pitching champagne yeast. My concern is that it'll attenuate too dry. Is there a way to get it just right? A calculator somewhere that would tell me how many grams to pitch?

I'd initially pitched two rehydrated packets of Mangrove Jack's M03 Newcastle Dark Ale yeast. The literature warned that attenuation would be a problem with higher alcohol beers and suggested that lowering mash temp might help. I did, but it didn't, at least not enough. The M03 has given it a nice flavor profile, but it would definitely benefit from a lighter body and higher ABV.

Many thanks!
Dave

I'll post my results for posterity...

By day 5 my wee heavy had fermented from 1.095 to 1.037. On day 7 it was still at 1.037, so I pitched half a packet of Red Star champagne yeast, non-rehydrated. Again, my concern was that it not ferment it too dry. Airlock activity picked up again then slowed. By day 9 it was at 1.032 where it stayed. On day 12 I pitched a second new half-packet of Red Star champagne. Airlock activity never picked up again and SG remained at 1.032.

My two-part prognosis as to why I couldn't ferment it further is that the consumable sugars were spent. While there's still a lot of malt character in the beer I sampled, its sweetness is likely coming from longer-chain sugars that brewers yeast isn't going to get at.  AND/OR... I was asking the champagne yeast to go to work in an already high-alcohol environment without rehydrating and at an improper pitching rate. Had I rehydrated and pitched the full packet I'm pretty sure I would have fermented it closer to the 1.024 I was aiming for. But please, anyone who knows better is welcome to add their US$0.02.

The upshot: Though I aimed for an FG of 1.024, the beer I sampled at my last gravity reading was well balanced with a nice warm alcohol nose. Another 6 points off the SG may have made the alcohol too hot.

Champagne yeast does great with fruits (fructose sugars) and can handle ABV's up into the low 20% range.  It's not good at long chain Barley sugars though.  You'd have had more success by making a starter with Wyeast 1728, which can handle high ABV environments and pitching that.  Your flavor profile was already set with your original yeast and the Wyeast 1728 wouldn't have affected the flavor much.

The 1728 would have been able to handle the stuff that your original yeast and champagne yeast couldn't handle.

My strong Scotch ale is a little lighter on the OG (1.088) and attenuates down to 1.024 using WY1728 and a three week primary.  I start out with fermentation temperature at 64F and slowly allow it to rise to around 68F after the first few days.  I bottle it and store it in the basement at temperatures of around 50F (winter) to 62F (summer) for at least 3 months.  Before that, it does come in with a distinctive alcohol finish and bite, but given the time it will mellow out nicely.  This is one recipe that I brew for next year's consumption (when I can resist).

So give it some time.  The yeast (WY1728) can handle the higher alcohol content but it definitely slows the activity down and kind of drags into the finish.