replaced the regulator a while back and yesterday wife let window down and heard a pop and tried to go back up.glad she didn't keep trying,even though she had to drive about 40 miles home in 32 degree weather with the window 1/2 way down.the problem-3 of the 4 pop rivets that hold the regulator to the door had sheared off and the window was pointing down towards the front.i didn't get the replacement rivets from volvo,they were the right size,but came from napa.this time i used nuts & bolts to re-secure.time will tell if they hold.
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92-965-211k, 94-965-215k, 92-944t-205k, 83-242dl,totaled(8/04), 84-242GLT,totaled(2/03),83-245GLT,retired(03)

i did use lock washers.it's a ton of fun getting the nuts on 2 of the bolts,if you insert the bolts towards the inside of the door.fingers need to contort a bit,and then there's the conversation you have with door while picking the nut and washer back up,to try once again.
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92-965-211k, 94-965-215k, 92-944t-205k, 83-242dl,totaled(8/04), 84-242GLT,totaled(2/03),83-245GLT,retired(03)

the bolts will definately be much stronger.my concern would be the nuts working loose with the up and down stress.they're on very tight and i had to use what i had late evening.didn't think about locktite.
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92-965-211k, 94-965-215k, 92-944t-205k, 83-242dl,totaled(8/04), 84-242GLT,totaled(2/03),83-245GLT,retired(03)

I didn't use loctite either but did use a lock washer. The rivets are an inherently weaker fastener and lend themselves to weakening under the torsional stress and deformation of the inner door skin. Nuts and bolts are a much stronger fastening system. Even the use of any kind of washer serves to spread the stress over a larger surface area than a simple rivet. It'll be fine.

Did exactly the same thing about 18 mos ago. Driver side regulator was resecured with nuts,bolts and lock washers. Haven't heard a peep or vibration since then.