Flue pipe connection query

[dkw1972]

Hi all, I have a reducer to connect a flexible flue liner to the vitreous pipe from the stove. The reducer is the type with the 3 x pre drilled holes in the outer skin for self tappers, can anyone tell me if the length of the self tappers should just be enough to grip into the flexi liner? Or should they pass through the inner skin too? 
 

Also the woodburner previously only had around 300mm of vitreous enamel pipe before connecting to the flexi (short length of flexi into the flue). I’m lining the flue completely but can also only get around 300mm of vitreous pipe from the stove before the flexi. I could increase this if I made the transition further up the flue, is this something I should be doing? 

 

many thanks in advance. 

[limecc]

You probably did this job by now. It doesn't matter if the the tappers break through, in fact it's preferable.

 

You can get an extra long stub adapter which are quite useful in your situation.

https://www.stovefitterswarehouse.co.uk/products/long-nose-flue-adaptor-no-bolts-in-high-quality-stainless-steel-beware-cheap-and-thin-versions