We use a trunk with 2 interfaces and this is what we ended up doing. We don't need the 2nd 10 gig interface active so we only have 1 interface up per trunk and this is working ok.
The weight we assigned was 60 and we have 2 interfaces so each interface has to be up to get a weight of 60, with 1 interfaces down the weight is 30 and on the active unit you add the active bonus making the total 55 on the primary as shown here and the highest score becomes active.
LTM1:Eval:Active:In Sync] config tmsh show sys ha-group HA1
Sys::HA Group: HA1
State enabled
Active Bonus 25
Score 55
On the standby it looks like this
(LTM2)(cfg-sync In Sync)(Eval:Standby)(/Common)(tmos) show sys ha-group all
Sys::HA Group: HA1
State enabled
Active Bonus 25
Score 30
Consider when you activate the 2nd interface in the trunk. Now the full weight of 60 is added to the active bonus of 25 so that would be a score of 85 and the standby would be 60. If you lose 1 of the 2 trunk interfaces on the active the score changes to 25 + 30 or 55 which is lower than the standbys 60 so a single interface failure out of 2 in this configuration would trigger a failover. Consider how you want this to work fail over from 1 interface or both? So when we do activate the 2nd 10g interface we could increase the bonus to 35 so the one interface weight of 30 + active bonus 35 (65) would still be higher than the standby which is at 60.