Without seeing a full picture of the boat, with the mast rotated from full on side view, front and looking up the boom, it's impossible to shay what is wrong.

5 - 7 seconds is not THAT extream.

As I stated abouve. WH results from an unbalanced boat. Could you take a few pictures showing the WHOLE boat from one side with the sails up and mast rotated correctly; same from the front (again showing all the boat). Same from the back shwoing the whole boat, same from the back, but focusing on the sail (please sheet in to "normal" upwind tensions) and finally lying on the tramp, looking up the sail, ideally showing as much of the sail as possible.

ALL with mast rotated. and main sheeted in.

IF you have the time can you do all the above for the following settings

1, Light wind setting - Downhaul on just enough to take most horizontal creases out; mainsheet as you would have it for sailing up iwnd
2, Medium wind setting - Downhaul on "medium" and sail sheeted for upwind
3, Strong wind setting - Downhaul on MAX and sail sheeted for upwind

Remember to also change the outhaul to the proper setting for upwind in each one.

this will give a total of 15 pics

Side, front, bacl all boat, back just sail, lying on tramp looking up for Light, med and strong wind trim.

Cheers

Simon

5 to 7 seconds for the boat to round up in nice wind.. That is not bad, that sounds about perfect to me. Move the crew a bit forward and you will track straight.
A natural round up can be a safety feature if you fall off the boat.

Thanks to all
I will try to apply the councils and will make the photos as soon as possible.