hiya i have looked at your minis harness i think you should change the bridle as there is no nose band dispence with the over check as you could make problems.
your pad driveing saddle has fixed tugs that is another problem as the harness can move and rub your mini and the shafts have no independent movement and also ajustment to balance is nill.
that is the main important thing is ballance.
when you drive the tugs move independantley and the tug buckles make a chinking noise as thay lets say chatting to you so you know there is compleat ballance.
may i sugest take the harness back and get another one.
your bridle poll strap browband winkers (blinkers) throat lachs face drop and rossettes.
your existing bridle if you titen the overcheck the blinkers will impead the ponys eyes and problems will also start there.
other bridles have a strapfrom the blinkers through the loop in the brow band to the poll strap that keeps the blinkers away from the eyes.
ill be honest revaluate the harness you have got.
if you need any help honestley i wish i was there to help you my frend and all thoes that want to drive as well.
i have diagrams that can help in my albums hopfully you will understand more from them.
if need be i can post pictures of the bridles i have and tricky will gide you to see how the harness fits many thanks and i wish you the best michael.