Specifying a filename for the FMODEL ends with error CFTU26E trying to open that file.

Fopen routine is used to open the file and with the standard C routine we use, quotes 'my.file.name' are mandatory at Fopen time.
Actually, CFTUTIL commands interpreter removes quotes and then, try to open an un-quoted filename.

The workaround on the MVS batches is to open the FMODEL file using a from DDNAME reference:

//FMODEL  DD  DISP=SHR,DSN=my.file.name(DSPCNF)
//CFTIN   DD  *                                      
 DISPLAY PART=LOOPTCP,                                  
         FMODEL=DD:FMODEL

The syntax DD:DDNAME will refer to the JCL related DDNAME to open the file
The DDNAME can be of any name

Future CFT versions may include an enhancement to allow opening files from following syntaxes:

$DDNAME --> ref. to a know JCL DDNAME

DD:DDNAME (for compatibility)  --> ref. to JCL DDNAME

and with fully qualified FileName --> part of a CFTUTIL commands interpreter expected enhancement