Interesting tatic. Not what I personally use against an ISD, is what I thought the TRD would be.
I go about 6km from the ISD. At this point the fighter should be level with the end of the ISD. This is where I begin my approach. There will be some dodging but to avoid this pitch your fighter up and down.
Now once you reach the ISD you will notice a trench more or less on each side. This is the runing part of it. The guns cannot reach you will your in there so you have a nice straight run in which to straife. However if they block your weapons don't worry this isn't the main part of the attack.
Now after flying through the trench I come to the engines. You will take very little damage (if your in a Tie Defender or advance you don't have to worry), with Regular T/F, angle the fighter so that it is just above the engines you should take no damage if you do go a little higher. the Guns won't target you. Then there is a sweet spot right behind the command tower. from there you match speeds with the ISD rotate your fighter, and you will see the top of the shield domes. you then can knock them out at your leisure. Then site back and blast the ISD with no fear.
With a shielded craft usually I fly along the hull taking out the gun implacements and engines.
"Dulce bellum inexpertis."
(Sweet is war to those who have never experinced it.) Roman Proverb