A small Bruce will be by far the best option. with a Bruce you can often get away with a smaller size ..............
Prob 1kg Bruce, 2m of 6mm chain, and 100m of 6mm 3 strand nylon warp ......... that will all fit nicely into a bucket for easy storage.
A drogue can also be useful to cancel the effects of wind when at anchor.
With my 4.2m RIB, I use a 1kg Bruce, 3m of 8mm chain, and 220m of 8mm warp .......... I often anchor in 75ft of water with a 2knt+ tide rip .........
Anchor from the bow eye and use a lazy line as a painter out to an A2 /A3 buoy............to set the amount of warp just tie an Alpine knot.
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