Most drysuits started as copies from known brands like DUI , then analysing theirs failures ( crotch sewing , arm valve position , arms position (forward instead - classic down - santi ) , material elasticity and breathing properties , then well known problems with glue type and prepairing material surface for glue (ursuit ) ..... a tons of problems to solve in real life.
As you are from Italy search for AQUA3 in Trieste ( they make wetsuits , buoyncy compesators , drysuits and some killing rebreathers )