Well, I guess restraining rotations, RX, RY, RZ between node 30/31 will not make much difference as 1020 is connected to node 40 with C node hanger; hence effects of X, Z movement of 1020 shall not be transferred to node 40 and subsequently 30. You may try in model and tell if results are different.

I shall also suggest weightless rigid element at ambient temperature as suggested by Naren. You may, however model dummy pipe on which hanger shall be mounted for more accurate results. Also the support configuration drawn by you is a very common vessel clip support arrangement and by experience, I do not envisage any problems of angularity in the hanger due to lateral expansion of the column or axial expansion of trunioun. You may reconfirm by manually checking if tan-1(|horizontal disp of spring node (1020) - horizontal disp of spring pivot pt (30)|/height of hanger) is within 4 deg.