Hi, it's great things went well for a while
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The 2-1 is a tricky time, well it was for me and my DS! I envy those who find a smooth route through the transition. The thing to remember though is that you *will* get through it even if it's a rough patch, eventually the routine does work out and settle back down again.
I would say, looking at your times, that now might be the time to make the leap to 1 nap. You already have a feeling of moving the first nap a bit later which would help with a resettle or a W2S to get a longer nap, and as soon as you get a longer nap it becomes hard to fit in that CN so instead you go for EBT.
Your routine might look something like this:
WU 5.45
A 5hr
S 10.45/11 - 1.00
A 4 hr
BT 5.00
Although like I said, it is not always smooth going. My DS suddenly stopped doing his regular 2hr nap when we dropped to 1 nap and was doing 20 mins OT napping instead, my only option was to W2S or resettle as many times as I could to get some sleep into him and eventually he settled back down onto his 2hr nap.
Moving to 1 nap *can* mess that nap up because of the OT involved, but there may not be other options which work any better.
If your LO is okay with a capped CN (is see he was grumpy when you capped the CN, this is okay if he recovers relatively quickly though with some cuddles and time to wake up) then you can keep capping it shorter and shorter over the coming weeks keeping in mind that he might be grumpy after that CN.
It may also be an option for a short time to allow a full CN but to move BT later. This could work for a little while because you may then get a slightly later WU in the morning and gradually the first nap moves a bit later etc. Clearly you can't do this indefinitely as WU and BT both move and need to stop at a reasonable time...but it could get you through a couple of weeks and by then he may be more able to cope with a longer second A time and then EBT or a capped cN. A few weeks different in development really can make a difference to the ability to cope with tiredness.
So there are a few ideas there for you to think about, only you really know what will suit your LO best or what you prefer to try.
Personally I would not switch to a short am nap. I would maintain the habit of a long nap as much as you possibly can, encouraging that nap to lengthen and move later in the day...it eventually comes at late morning/lunch time and as he gets older it may be in the early afternoon.
Keep in mind too that whilst on 2 naps your LO is unlikely to do a longer night. When you cap the CN or cut it out and move to 1 nap your LO will likely extend the night sleep. You might see 12 hrs per night rather than the 11 you currently get.
Hope this helps some