[Shiraz (Ray)]

I can't see any reason why well depth is an issue at all. I think that, provided you don't overexpose by using excessive sub length, the star profiles will be exactly the same for pixels with small wells or large wells. They will look bigger if the pixels are small, because there will be more pixels under the star profile, but the shape will be the same.

Well depth is a factor in star shape if you use subs that are too long - and then you will saturate the cores and bring up the dim skirts. This is easy to do with chips with small wells if you try to use long subs (eg with your 694 and typical optics, anything much over 5 minutes in luminance will probably be too long) - but you don't need to use long subs if the read noise is low and the dynamic range will still be good with short subs. If stars are being wrecked 5x faster with small pixels, the answer is easy - use subs that are 1/5 as long and have 5x as many of them.

DSLRs have well depth equivalent to CCDs, but they end up with white stars because users have wound up the ISO to get better looking subs. In the process, they reduce the effective well depth, throw away most of the dynamic range and end up with most stars saturated. High sky signal can also take over much of the remaining dynamic range, doing even more damage to the stars. This can be fixed by using low ISO, using short subs that keep the sky noise well to the left of the histogram, forgetting what the individual subs look like and concentrating on the final stack. However, new users fall into the trap of trying to get the subs to look nice - and they end with saturated stars.

Edit: It would be very helpful if you could post some images showing the difference between your two sensors.