M_Boats: Porta-Potta measurements on M-15

Kendall Docter from Bossier City, LA. #164 measurements for the Porta-Potti hole are as follows. 15-5/8" Front to back. The hole is not rectangular. Towards the stern,it is 11 -5/8" Closer to the bow it is 12 5/8" Does anyone have a serial number close to #164 they could measure? I have found several "135 " models on eBay but dimensionally some of them look different and I'm hesitant to purchase something that won't fit. (Thanks EinkaufR43@aol.com M-15 #249 for your previous response)