Hi Mike,
Depending on your development for this film,you should not notice any loss of detail in the highlights with one stop over the "NORMAL" EI. Films such as this have generous latitude to over exposure and may actually look better !
If the images are of an unrepeatable nature and you dont want to lose them, shoot another roll at EI 200 and use this as a test before commiting your valuable shots to dev. Try developing the dummy roll at your normal time, and see. If the resulting negs look too dense then back off dev time for the important shots, (say-20%).
Regards, John.