well,i do know that in truespace that when you "mirror" the said vertexs,you must make really sure that the polys that are going to meet are perfectly flat on that axis,if not,then when you mirror or dublicate the said object it will not meet correctly,so after you finish with the first half of the model you need to go to the side views and look to see that they do in fact reach the same axis,if not drag them back to the place where your plane began and if it distorts the rest of the polys then you will need to re-move them to what your intent is for your fishy...my next message will hope illustrate this