u need a shroud that separates above and below the frames (i have one built from thin ply) u can cut and shut a suitable 60 size one or make a plug and do up a glass one (my choice ) instead of ending the shroud u must take it past the cylinder and head then make a 90 deg bend to channel the hot air out of the fuze ,a piece of piss really , and an aircraft head was all that was used in the early ones ,