How to do OQPSK Demodulation in MATLAB 2020b without using inbuilt block?

I want to do modulation classification among OQPSK and QPSK. For that I require downsampled constellation (samples per symbol=1) of OQPSK. I am unable to get that in the comm.OQPSKModulator and comm.OQPSKDemodulator block of MATLAB 2020b. So I modulated the signal on my own by following steps:

a. Split bits to odd (I) and even (Q)

b. Filter both I & Q streams, e.g., with raised-cosine or half-sine filtering

c. Delay the even-bit stream (Q) by half a simple and make a complex waveform I + j*Q

Now I want to demodulate it. Please tell me the correct steps so that I can get downsampled constellation before demodulation.