1.5 - 1.75 spacers don't put too much stress on the bearings. I have seen 45mm spacers for sale, but it set up an account with a bearing suplier with those. As long as you buy billet spacers, your good to go. When I fitted my spacers, I set the torque wrench 20Nm higher (IIR 110Nm) and used stud lock on the threads. Stud lock is a more permanent set than thread lock. I've checked them a few time since fitting, nothing has moved nor loosened. I'm running 1" spacers with offset modular rims & 10.50 tyres, so have around 3.5" - 4" extra track.