The chain is so very important as it is what keeps your anchor in the right holding position. I know it's a pain to drop anchor and even worse to pull it seeing one has to lean over the bow to lift it strait up so as not to scrape the glass. Your boat may not have the room in its anchor locker for that much chain but if you have to go with 3/8's instead that may be even better, it sure weighs a lot less. 300 feet of rhode is usefull on bigger boats as windage scope is all important but I think 100 feet and 30 feet of chain will give your anchor a good angle for holding power in up to 25 feet of water, remember that chain is going to drag along the bottom and your anchor flukes will have a chance to reset. With little chain and lots of rhode your chain may not be heavy enough and angle up towards your boat along with line and that means disaster.
Two weekends ago I watched two boats one 24 feet and the other 18 feet drag anchor when the wind did a 180 and came up at 25 knots. The anchors they had were Danforths about the right size but they only had 10 feet of chain. Both boats had a strong set and held firmly till the wind changed dirrection This made it impossible for the anchors to reset long enough for the owners to get back out to their boats as they were on shore claming. If you put out all 300 feet of rhode you will set your anchor very nicely indeed but that means you need plenty of room if you swing. I would worry without the extra chain that the anchor would skim along the bottom especially if the she let go on a fresh breeze blowing off shore with the bottom angle dropping into deeper water. I guess I feel lucky in having 300 feet of 5/8 chain, a 65 pound Bruce and a windless. When the wind changed dirrection that day I was still on board. Once my chained tightend after the 180 swing it took about 10 feet of drag before I reset long enough to get the engine started and reset for real. The two other boats luckily went out into deep water and the owners had an inflatables with outboards to go retrieve them. Experience is the only thing that can make you feel confortable when leaving your boat after anchoring, lot's of practice helps. Both of those owners went out last week and got more chain.