Wouldn't you do something like this (?) :

In iax.conf :

[iaxRpt_1]
secret=foo_bar
type=friend
host=dynamic
disallow=alliax.conf :
iax.conf :

[iaxRpt_1]
secret=foo_baiax.conf :

[iaxRpt_1]
secret=foo_bar
type=friend
host=dynamic
disallow=all
allow=ulaw
allow=gsm
allow=g726aal2
codecpriority=host
context=radio-gui_1
requirecalltoken=no
jbenable=yes

[iaxRpt_2]
secret=bar_foo
type=friend
host=dynamic
disallow=all
allow=ulaw
allow=gsm
allow=g726aal2
codecpriority=host
context=radio-gui_2
requirecalltoken=no
jbenable=yes

iax.conf :

[iaxRpt_1]
secret=foo_bar
type=friend
host=dynamic
disallow=all
allow=ulaw
allow=gsm
allow=g726aal2
codecpriority=hostiax.conf :

[iaxRpt_1]
secret=foo_bar
type=friend
host=dynamic
disallow=all
allow=ulaw
allow=gsm
allow=g726aal2
codecpriority=host
context=radio-gui_1
requirecalltoken=no
jbenable=yes

[iaxRpt_2]
secret=bar_foo
type=friend
host=dynamic
disallow=all
allow=ulaw
allow=gsm
allow=g726aal2
codecpriority=host
context=radio-gui_2
requirecalltoken=no
jbenable=yes


iax.conf :

[iaxRpt_1]
secret=foo_bar
type=friend
host=dynamic
disallow=all
allow=ulaw
allow=gsm
allow=g726aal2
codecpriority=host
context=radio-gui_1
requirecalltoken=no
jbenable=yes

[iaxRpt_2]
secret=bar_foo
type=friend
host=dynamic
disallow=all
allow=ulaw
allow=gsm
allow=g726aal2
codecpriority=host
context=radio-gui_2
requirecalltoken=no
jbenable=yes





extensions.conf :

[radio-gui_1]
exten => 27783,1,rpt(27783|X)
[radio-gui_2]
exten => 27826,1,rpt(27826|X)


extensions.conf :
allow=ulaw
allow=gsm
allow=g726aal2
codecpriority=host
context=radio-gui_1
requirecalltoken=no
jbenable=yes

[iaxRpt_2]
secret=bar_foo
type=friend
host=dynamic
disallow=all
allow=ulaw
allow=gsm
allow=g726aal2
codecpriority=host
context=radio-gui_2
requirecalltoken=no
jbenable=yes

In extensions.conf :

[radio-gui_1]
exten => 27783,1,rpt(27783|X)
[radio-gui_2]
exten => 27826,1,rpt(27826|X)