I don’t know the answer but I’ve heard of people managing this somehow.
Doris on earlybay.com may be able to help you – he’s a full on fountain of Dormy knowledge.
There’s a chap at Dormobile who is also knowledgable on early dormy stuff, very helpful but I’m afraid I’ve forgotten his name – contact them through http://www.dormobile.co.uk/ if you haven’t already tried.
I’d be interested to know how you get on, good luck!
JB