/lastsynth <wait25>
/lastsynth <wait25>
...
etc. Just adjust the wait time to whatever is needed and that your connection allows. I normally pad my /lastsynth spam macros by 1-2 sec due to missed synths from the "you can not do that yet" error being far more annoying. It's also a good idea to set up stuff like Trust macros to work without haste and baseline fast cast.