I have a similar Dilemma. I run my shop with a part-time member of staff, who will be going off on maternity leave in July - leaving me on my own. I currently open 9-5, but she had a week off recently, so I tried out some new opening hours of 9.30 - 4.30 but found that it took me longer than I thought to get all the deliveries done and ended up opening 10-4.
I found that as long as the customers knew (put a sign on the door and a message on the phone) they were ok about it, but if you're worried about losing trade its probably best to find someone to do deliveries for you. We're in a fairly small town that doesn't really have many people about before 10 or after 4 anyway, but it would depend on where you are based and your areas trading patterns.

Sarah

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