I am at a loss as to why you would do this.
There is no rubric governing the posture of the laity at this moment other than that they should be upstanding.
As the US Conference of Catholic Bishops notes regarding both the posture during the Eucharistic Prayer and the Our Father:
Should people stand or kneel during the Eucharistic Prayer?
*This is answered in the General Instruction of the Roman Missal, number 43:
In the Dioceses of the United States of America, they should kneel beginning after the singing or recitation of the Sanctus (Holy, Holy, Holy) until after the Amen of the Eucharistic Prayer, except when prevented on occasion by ill health, or for reasons of lack of space, of the large number of people present, or for another reasonable cause. However, those who do not kneel ought to make a profound bow when the Priest genuflects after the Consecration. The faithful kneel after the Agnus Dei (Lamb of God) unless the Diocesan Bishop determines otherwise.*
Some people hold hands during the Lord’s Prayer, while others hold their hands out like the priest. Is there a prescribed posture for the Our Father?
No position is prescribed in the Roman Missal for an assembly gesture during the Lord’s Prayer.
usccb.org/prayer-and-worship/the-mass/order-of-mass/liturgy-of-the-eucharist/posture-during-the-eucharistic-prayer-and-our-father.cfm
The last I knew – I am a priest of Europe – there was only one diocese in the United States where the Diocesan Bishop initiated particular law on this point, which is of course his right; the Diocesan Bishop is the supreme moderator of the liturgy in his diocese.
How those in the congregation, assisting at Mass, are positioning their hands at the Our Father is of no concern to either the bishop or the priests in my diocese…presuming the laity in question are not using their hands in the moment to strike their fellow parishioners.
As a parish priest, yes I would have found it alienating if someone who had just been welcomed into the parish began attempting to correct my parishioners, least of all on a matter they were quite free to do.