I think they look pretty cool.My first 3 or 4 Guns were Francottes ..20Es all from around the 30's,I think most of them had side clips....no blood shed here.They were all 7 1/4 LB + "Pigeon weight Guns" .They seem like a nice extra touch that the builders went to the trouble of adding, they must have been tricky enough to fit nicely.Though to tell you the truth I could detect the odd slight bit of dreaded daylight on one side or the other on most of them .So perhaps they were more for show than actually helping side movement of the bbls...but there again, perhaps they were a perfect fit 70 odd years ago.
The two Guns..again Pigeon weight, that I have now don't have em.
A 1901 Greener Hammer Jones action & a nice belgian no name from 1926,7lb 10oz.. locks by Britte,stocked to fences,English bbls, bushed pins, Purdey 3rd bite & hinged trigger, but no sideclips
I must admit I find them comforting when present...just a little extra touch...but i don't think they are essential
good luck
franc