FB's concern about rider weight is well founded. Speedplay offers optional Ti spindles on it various pedal models and specifies a maximum rider weight of 185 pounds for them. And, remember, these are a factory item, not an aftermarket part designed by an unknown outside supplier. Even if you manage to find the Ti spindles for your Wellgos, how much faith can you have in them?

BTW, if you really want super light pedals, consider the Speedplay X or Light Action series. With Ti spindles they are about 150 gm/pair and you can trust their strength if you are within their weight limit.