Hi Peter,

Here is the ruling from the USGA...

5-1/4  Status of "X-out," "Refurbished" and "Practice" Balls
http://www.usga.org/Rule-Books/Rules-of-Golf/Decision-05/#5-1/4

Q. What is the status of "X-out," "refurbished" and "practice" balls?

A. "X-out" is the common name used for a golf ball that a manufacturer considers to be imperfect (usually for aesthetic reasons only, e.g., paint or printing errors) and, therefore, has crossed out the brand name. A "refurbished" golf ball is a second-hand ball that has been cleaned and stamped as "refurbished."

In the absence of strong evidence to suggest that an "X-out" or "refurbished" ball does not conform to the Rules, it is permissible for such a ball to be used. However, in a competition where the Committee has adopted the condition that the ball the player plays must be named on the List of Conforming Golf Balls (see Note to Rule 5-1), such a ball may not be used, even if the ball in question (without the X's or without the "refurbished" stamp) does appear on the List.

In most cases, "practice" balls are simply listed, conforming golf balls that have been stamped "Practice," in the same way that golf balls often feature a club or company logo. Such balls may be used even where the Committee has adopted the condition that the ball the player plays must be named on the List of Conforming Golf Balls.

Thank you Mike.  That was most helpful and a great relief.

Peter

It also shouldn't be a problem as the practice balls will perform not as good as regular balls