the wings on the outside of the nacelles? I made those from scratch stretching out a simple box - stretched and skewed. Since there are so many angles of the ship available you can get a feel of their position (as in how far they are below the saucer, that they appear to extend to a position nearly parallel to the width of the saucer, positioned the front line of the wing with the back line of the pylons and so on), I feel what I got as a a result feels rather accurate.
Otherwise, the Intrepid seems to be an older model Starfleet vessel (pre-Warp5) and therefore has different nacelles because of that. In fact to make the ones I have on my Intrepid was to use those of the NX and expand the width and height of the nacelles (not the length) by 130% (arbitrarily chosen) of normal size.