Is it possible to upgrade Singapore Airline flights using Velocity or KrisFlyer miles but credit flights to Velocity for status credit?

Dear Points Hacks,

My fiancé and I will getting married shortly and going on our honeymoon. As part of our travels, we have a flight from SIN to FCO and returning MXP to SIN (multi city ticket). We have a large (for us) cache of American Express Membership Rewards (about 300,000) and were hoping to do that segment in business class.

We have currently purchased premium economy tickets (fare bucket P) which were sold with the ability to upgrade with miles but when I try to upgrade, the button allowing upgrades is greyed out and informs me that the ticket is not available for upgrades. I was thinking that this might be because we have both put down our Velocity numbers instead of our KrisFlyer numbers and I have heard that SQ only allows upgrades for KrisFlyer members?

My questions are as follows:
(1) Am I correct in assuming the reason I cannot upgrade is because the system is not aware we are also KrisFlyer members?
(2) Is it possible to upgrade using KrisFlyer miles (i.e. modify our booking with our KrisFlyer numbers) BUT still award status credits to our Virgin Velocity (for example, changing the account we credit at time of check-in?)

NB. We fly Virgin a lot more and would prefer our status credits flowed there.

Thank you in advance!

PS. I am new here and this is my first post so do excuse any inaccuracies I may hold.

  1. I believe you need to be logged in as a KrisFlyer member to upgarade. Then it will show you points required. Ideally you want  a saver upgrade for better value.

  2. it is possible to make the booking with Singapore KrisFlyer then in “manage my booking” change to your velocity number under “your details”, I have done this with no issues.

Phoning KrisFlyer to do all this possible too, they are usually very helpful and don’t mind if you credit the points to velocity.

Good luck!