I strongly recommend that you not "vent" your feelings about any aspect of your supervision including the payment plan. You should make a good faith effort to comply with the payment plan, and most important of all make sure you make some payment monthly. Sporadic payments will not win you friends in probation and may lead a Court to believe you are choosing not to pay. Keep accurate records of your financial circumstances so you can demonstrate, if need be, that you are doing the best you can. It is especially important to establish a good relationship in the beginning with your PO--venting is certainly not the way to start off that relationship.
Probably not a great idea to vent on them, at best they will ignore the rant at worst it could create some issues for you. You have a right to challenge the amount of the restitution if you feel the number isn't correct. If it is but you can't afford the payments you can ask for lower monthly payments. What ever you do make sure you pay something to show you are making an effort.
This information does not create an attorney /client relationship and should not be use or relied upon to make any decision in your case. Only consultation with your own attorney can provide you with the advice you need for your case.
My colleagues have it right. As long as you are making a good faith effort to pay, you will not be held in violation. The court could extend the length of the sentence to give you time to pay. Good luck.
I agree completely with my colleagues on this one. Venting will accomplish nothing and could likely result in more complications to your situation. I would suggest you retain a competent lawyer who could file a modification on your behalf. Good luck.