At the Easter Vigil we are able to reduce the number of readings and psalms, but can you shorten the psalms?

I have experienced the Vigil having all of the readings, but only the minimum number of psalms were used.

Now, this year the new idea being proposed is use all the readings and all the psalms, but only the first verse of each psalm. Is this in any way permitted?

There is a loosely related old thread here:
http://forum.musicasacra.com/forum/discussion/1086/cutting-verses-from-psalms/p1

The thing about the Vigil is, if you can omit a reading and its psalm response entirely (and you can), it seems that under the principal that "he that can do the greater, may do the lesser" you could then choose to omit part of the psalm (but that seems to invite being able to omit part of the readings at will, which seems plainly dangerous). However, the rubrics seem to require three of the readings, so it seems at least three of the psalms should be used in full.

In particular, the reading from Exodus with its Canticle is never to be omitted, so at the very least it seems that after the reading of Exodus 14 the full canticle from Exodus 15 given in place of a psalm should be used.

I am merely a volunteer, not the person in charge, and in fact in this case the pastor and music director seem to be on different pages, with the pastor wanting all of the readings, and the music director thinking we need to keep the length down for the cantors and people. I don't really want to get in the middle of this, but on the other hand I would hate to see the Vigil become a cause of friction between the music director and pastor.

I think I am going to offer the following suggestions, but am interested in other thoughts:
1. The full Exodus canticle as given should always be used.
2. It might in future be better, if necessary to shorten the psalms, to sing them directly through all the verses, so that the responsory is only sung at the beginning and end rather than between the verses. That would seem a reasonable compromise.

Thoughts?

Here is what seems to be the relevant section of Paschalis Sollemnitatis:

85. The readings from Sacred Scripture constitute the second part of the Vigil. They give an account of the outstanding deeds of the history of salvation, which the faithful are helped to meditate calmly upon by the singing of the responsorial psalm, by a silent pause and by the celebrant's prayer.

The restored Order for the Vigil has seven readings from the Old Testament chosen from the Law and the Prophets, which are in use everywhere according to the most ancient tradition of East and West, and two readings from the New Testament, namely from the Apostle and from the Gospel. Thus the Church, "beginning with Moses and all the Prophets" explains Christ's Paschal Mystery.[90] Consequently wherever this is possible, all the readings should be read so that the character of the Easter Vigil, which demands that it be somewhat prolonged, be respected at all costs.

Where, however, pastoral conditions require that the number of readings be reduced, there should be at least three readings from the Old Testament, taken from the Law and the Prophets; the reading from Exodus chapter 14 with its canticle must never be omitted.[91]

86. The typological import of the Old Testament texts is rooted in the New, and is made plain by the prayer pronounced by the celebrating priest after each reading; but it will also be helpful to introduce the people to the meaning of each reading by means of a brief introduction. This introduction may be given by the priest himself or by a deacon.

National or diocesan liturgical commissions will prepare aids for pastors.

Each reading is followed by the singing of a psalm, to which the people respond.

Melodies should be provided for these responses which are capable of promoting the people's participation and devotion.[92] Great care is to be taken that trivial songs do not take the place of the psalms.