H Jo,
Looking in the OS web site ,I found a O.S. 50 SXH . Never have seen a Thunder Tiger SXH . This is a very powerful motor ,and would fly your 40 sixe plane very well. It is a little heavier then the standard O.S.40-LA ,and as such -it would probably require a little weight in the tail,but I think moving the reciever battery further back would balance the plane fine. Looking at the picture of the motor ,prop shaft looks long enough. The only thing I noticed was ,I din't see a muffler. . Might be a problem. Maybe some one else knows what size muffler you would need ? Good Luck, Amelia