OK, so there are some options to check into.
I remember Koni stating the SPA-1s were "not for street use or big-block-powered cars", which means I used them for exactly the type of application they said not to.
The SPA-1 rebound circuit was adjustable, but the fixed compression damping was seriously on the light side. This let the front end dive back down (too?) easily, because the idea IIRC was to make sure the front end would settle on the top end.
One of the things I'm wondering is if the rebuilt SPA-1s would work better than the QA1 R-series (fixed firm compression damping & adjustable rebound damping) I replaced them with. The R-series have extremely light rebound damping on their lightest setting, so there's no problem getting the front end to lift. Whether the compression damping is actually too stiff, I really can't say. Since that circuit isn't adjustable on the R-series, ya' just gotta live with them if you're not willing to spring for a re-valving.
Also, I found the old (2007) e-mails I got from Koni America when I inquired then about having them rebuilt and they also mentioned being able to upgrade them to externally-adjustable rebound damping... for more $$$, naturally.
Brad