I just did that for Flat E. I extended the TV Attena from one side of sitting room to the other side through the speaker duct. Then split the connection into two one feed into master bed room and the other to the second bed room through Telephone duct. I tested the signal level. No amplifier is needed. But lots of cable work to get them through the ducts.
One thing to watch out is that the Telephone duct is around 20mm but the speaker duct is around 13mm.