I've not been round the bill at Portland but understand that with wind over tide it can get quite confused. Sounds like with the neaps and wind strength you should be ok.
Worth checking the chart when approaching Witterings as the sand bank does extend further out than you would think if no experience of it... ( you've probably guessed why i've highlighted this

With regard to entrance into Solent, either follow the main channel in through the forts, obviously keeping clear of any larger vessels on transit or again, hug the coast by Hayling, eastney and up towards southsea. Be aware of the submarine barrier that runs out from the beach. A small boat channel is clearly marked.
At low tide, many of the concrete blocks are visible, shortly after they aren't but will quite easily take a drive leg off or do some serious damage if unaware.
https://www.google.co.uk/url?sa=i&rct=j ... 1811647783
https://www.google.co.uk/url?sa=i&rct=j ... 1811647783
Not much else to add i'm afraid other than i hope the sea trial goes well and you have an enjoyable calm transit back to its new home!!

Keep us updated.