So you are trying to move bond to IBKR SG, and keep your stock in IBKR LLC.
Just curious, if you sell your bond in IBKR SG, how do you move the SGD cash over to the IBKR LLC account?
I guess you are using DBSV cash upfront, ie. with a personal account? You can use FSMOne to sell from CDP, and their commission is very low (flat $8.80 + clearing fees). There are benefits in using CDP as well (rock solid stability, no custodian worries). If I were in your shoes, I will skip IBKR SG, and just use FSMOne to sell from CDP.