Rule 86 is attached. The better and easier way (since most units in Texas are voluntary in nature) is to limit the unit size by some formula related to drainhole length. Remember that proration units, density (spacing) units, etc. have no effect on title. Only the pooling transaction, MIPA or a community lease or fieldwide unitization does.
In the pooling transaction in most unaltered lease, it allows unit sizes to be increased to conform to those "prescribed or permitted" by the regulatory agency in order to obtain a full allowable. Strike "permitted"
Here is some sample language from one of my forms:
(d) If the well is classified as a horizontal well under the Rules and Regulations of the Railroad Commission then in effect, then the maximum size of the Earned Acreage Unit shall be determined by the following formula: 40 + .024 X L, where L = the length of the horizontal lateral component of the drainhole of the well, from the first take point to the last take point.