Drysuit zipper is regularly maintained - cleaned and lubed with the DUI brand zip stickB...
You may want to consider padding your shoulder webbing with tubular neoprene webbing covering...DGX...$20. a pair...
Further...make sure your zipper is regularly cleaned/lubricated...I use Zip Tech on the brass teeth...''thick formula'' Armour-All on the fabric portion of the zipper...both sides...I spray a small amount into a cup...and apply it to the zipper with a small nylon bristle artists paint brush...
Works like magic...keeps the zipper in ''like new'' condition with no top edge fraying...indefinitely...
When ever I travel with the suit...my zipper maintenance kit comes along with everything else...
W.M...
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As for the Armour-All - you mean the same stuff as car products? https://www.amazon.com/Armor-All-Or...&sr=1-4&swrs=AF8ED2B6D861334A7409A7A17C657AA4
When you say "fabric portion", just want to confirm you are talking about the tape-portion of the brass zipper?