I've heard of people (mostly 240 peeps) drilling stock 4 lug hubs to 5 lug. Not sure how well it would work going 5 lug to 5 lug, because you wouldn't have a lot (if any) of metal between the old holes and the new ones, but it may be worth looking into. Personally, I would rather run on drilled hubs than bolting an adapter on and then bolting a wheel onto that. Seems like it's adding 1 more potential weak spot imo.

The other problem with adapters like the ones in the link is that they will more than likely also act as spacers and push your wheels out. Some cars can get away with it and can compensate via fender pulling and rolling. The volvo is pretty boxy, though, as you obviously know, so I dunno how much fender pulling you could get away with if those adapters push the wheels out.

If it were me, I would look into either drilling your existing hubs, or seeing about getting a custom set made.