Is It Advisable To Have Penile Implant And Lengthening Surgery?

Recently I had decided to have penile implant surgery, after a consultation with an Urologist that I had seen for a previous prostate surgery. He told me that I should have the implant first and at some time down the road he would complete the penile lengthening augmentation surgery by implementing a procedure to cut, not only fundiform and suspensory ligaments, but also to excise collateral ligaments, in order to make the penis completely free from attachment. This technique completely releases the hidden portion of the penis and improves the results of a penile lengthening augmentation surgery.
My question is – shouldn’t the penile ligaments be cut before penile implant surgery so that the proper implant length (size) can be determined or does it not matter what size implants are used for the surgery (one size fits all)
Can both surgeries be done at the same time if not, why.
My next question is – is there any down side to having the penile ligaments cut if so what are they.