Why not do the Grand by kayak? Self support. No Rafts. Simple. This is a much easier trip to organize, can take less time, and is cooler in the summer heat.
Packing any of these crossover boats is a joy compared to self support out of a standard kayak. The Jackson Rogue, the Wavesport Ethos, and the Liquidlogic XP10 all have well thought out cockpits for adding the gear. Doing a night or two is simple. Doing two weeks is a bit of a challenge. A few packing tips: Use the smallest possible drybags. Even Watershed bags, although sweet and dry, are often too big to fit the small spots. Take the smallest items and just throw them in the hatch. For the last few days I used off the shelf dehydrated meals, which lived in the hatch on their own.
Food planning is a great challenge for this trip. Think small volume. Straight noodles are better than curly ones. De-box everything to save space. Unlike most bikepacking or backpacking trips, weight is not that big an issue. For example, I took along 4 cans of pears and peaches for a special desert treat. Dave went for the total dehydrated vacuum packed system. Here is his layout, which was well rewarded by his ease in packing every day.
On the Grand, there are SPECIAL RULES for self support kayak trips, that kindly allow you to take less stuff. Request them from the GC permit office, but basically you can use a modified groover, no firepan in the summer, etc. We were shocked that they plan on your poops taking 40 cu inches daily, but indeed ours worked out to about 3/4 of that amount so they were not too far off.
Our trip was 11 days to Pierce Ferry. I think our trip consensus was that eleven days to Pierce was too short for 8 person trip. Perhaps with less hikes it would be ok. 11 or 12 to diamond would feel much more like a normal grand trip. We did all the “normal” stops- including about 2 hours of hiking each day, but always were a tiny bit rushed. We had flows of 6-11k, which is pretty darn low and we figured added an hour each day compared to 15k. The new normal for spring and fall? Next time I would do 13 or 14 to pierce. Or smaller group would speed it up by 30 minutes a day. We only had 8, so you’d have to be a real small group to speed up much. Pierce Ferry is about two extra days from Diamond (the typical takeout) – 55 miles. The road there is paved nearly all the way to the water, and it saves lots of Hualapai fees. The downside is the bizarre overpopulation of helicopters. But overall, I couldn’t be more enthusiastic about doing trips this way. If your group has the skills, I am sure you will love it.