Tandoori Lamb Sausage?

Seeking some collective wisdom?

I am a big fan of indian food, particularly tandoori, especially lamb
kebabs.

Talking with my local butcher he suggested he could make up 5lb of
"tandoori spiced" lamb chipolatas for me if I provided a tandoori mix to
add
to the meat.

His concern is that the sausauges would be very tough if all lamb and
suggests adding ****k fat and a little rusk. Personally I'd like as much
lamb
as possible to retaint he flavour.

Any suggestions as to what ratios things should be mixed?

TA