You'll end up with about 2.5mm of wall thickness after boring to 65mm (836)
These motors have been getting drilled out to 65mm for years and years and I'm unaware of anybody having any issues with that being done.
I guess that ideally, bigger/thicker sleeves would be better but "How much better and what will the benefits be?"
If the motor isn't going to be subjected to extreme use, I'd personally be inclined to bore out the stock sleeves.
Keeping in mind that if you decide to go with the thicker sleeves, the cylinder block will need to be bored first for the thicker sleeves and the top engine case will need to be opened up as well.
Mick