I intentionally started my two packages using solid BBs with the intent of switching to screened BBs after the two colonies were established. I have been venting with an upper entrance for several weeks.
My question is would you switch bottom boards at this point in the season if venting is not a problem?
OR
Wait until fall or early spring to switch to screened BB?
I guess it depends on your rationale for using SBB. If it is to control varroa, you may want to rethink.
http://forum.beemaster.com/index.php/topic,10753.msg105971.html#msg105971
If it is for ventilation, a slatted rack works just as well and allows the brood area stay warmer and more humid which is less advantageous for varroa and helps a faster/bigger spring build up.
Varroa is not usually an issue for a first year package. If it where me, I would wait until next summer, though in reality, I don't use SBB anymore.
rob....
While I like SBB, I also find that solid ones work fine. If you already own both, then I'd swap whenever you like. If you put a tray in you can control the ventilation fine. If you don't have the SBB yet, the solid will do fine. I've started converting them to feeders:
http://www.bushfarms.com/beesfeeding.htm#bottom