Is it safe to use the source address property to limit access to a VIP ?

Generally filtering by source IP address is not a good practice, but in reality a lot of people do it. You have to ask yourself what the risk is if your filter does not work, and what the real purpose of the rule is. If you are just trying to stop curious honest people from viewing the page before launch, then a source IP rule will probably work OK. If there is some greater risk involved then it might not be a good idea.

Another option might be to move it to another port temporarily. Let the firewall team open 443, but since you are running on 8443, no one can get to it(8443 is not open in the firewall, and nothing is answering on 443)