Your arms are not particularly short looking, only a little. I don't believe any doctor would ever do both arms and legs simultaneously. You need to use your arms to stretch while leg lengthening and for transferring. If you lengthen tibias your arms won't change relative to your torso or get farther from your knees. Yes vs total height they'd be shorter but I think they'd look fine. Safer to lengthen femurs and most good doctors strongly advise that if only doing one segment. You might look like your arms are too short with 8cm femurs and want arm lengthening after, not at the same time lol. Do some mocks up and decide what looks acceptable. Good luck .